Further cleanup/optimization of system_time

On gcc4, we can use the __rdtsc builtin. On gcc2, provide a similar
inline-able version of rdtsc, and remove the rdtsc function written in
assembly, saving a call/ret on every call.

There has been some discussion about performance, but note that this is
only bootloader code, it is not used when the system is up and running,
therefore performance is not that critical.

cpu: Extract shared x86 code from efi & bios_ia32

This issue was initially detected by PVS Studio (issue number V547) and fixed
as part of Google Code-in 2019.

The initial problem was the calculate_cpu_conversion_factor function
which had been copied in the BIOS and EFI versions of the boot code.
Further investigation led to more duplicated or very similar functions
being identified.

Introduce an arch_cpu.h for the x86 boot platform to group these things
in a single place, and adjust the BIOS and EFI code to call into that.
Note that the BIOS and EFI code is still a little platform specific,
ideally there should be a boot_arch_cpu_init() function for each
architecture as already done for openfirmware and u-boot.

Also remove some irrelevant comments from copypasted files for other
architectures, as that was filling my git grep with useless noise.

Change-Id: I16d815f0bf015cec0b4e03cc14f3cc447c7164c5
Reviewed-on: https://review.haiku-os.org/c/haiku/+/1985
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

* renamed smp_boot.c to smp.cpp
* there is now a "Disable Hyper-Threading" safemode in the boot loader
* the SMP & HT menu items are now added in smp.cpp - and are only added
if the system supports one of them.
* more cleanup to smp_apic.h
* removed cpuid() from the boot loader's support.S - instead, it will now
use the one from the kernel.
* added a very weak HT detection: if the MP config only listed one CPU,
and this CPU supports HT, we enable the other logic processor manually -
as this currently doesn't work, it's disabled, though.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@14536 a95241bf-73f2-0310-859d-f6bbb57e9c96

Renamed src/kernel to src/system.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@12359 a95241bf-73f2-0310-859d-f6bbb57e9c96

* renamed smp_boot.c to smp.cpp
* there is now a "Disable Hyper-Threading" safemode in the boot loader
* the SMP & HT menu items are now added in smp.cpp - and are only added
if the system supports one of them.
* more cleanup to smp_apic.h
* removed cpuid() from the boot loader's support.S - instead, it will now
use the one from the kernel.
* added a very weak HT detection: if the MP config only listed one CPU,
and this CPU supports HT, we enable the other logic processor manually -
as this currently doesn't work, it's disabled, though.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@14536 a95241bf-73f2-0310-859d-f6bbb57e9c96

Renamed src/kernel to src/system.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@12359 a95241bf-73f2-0310-859d-f6bbb57e9c96