MIPS16e2: Provide feature overrides for non-MIPS16 systems

Hardcode the absence of the MIPS16e2 ASE for all the systems that do so
for the MIPS16 ASE already, providing for code to be optimized away.

Signed-off-by: Maciej W. Rozycki <macro@imgtec.com>
Reviewed-by: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16097/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

MIPS: Correct `nofpu' non-functionality

The `cpu_has_fpu' feature flag must not be hardcoded to 1 or the `nofpu'
kernel option will be ignored. Remove any such overrides and add a
cautionary note. Hardcoding to 0 is fine for FPU-less platforms.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9694/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

MIPS: IP22: This platform may come with either MIPS III or MIPS IV CPUs.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

MIPS: Optimize current_cpu_type() for better code.

o Move current_cpu_type() to a separate header file
o #ifdefing on supported CPU types lets modern GCC know that certain
code in callers may be discarded ideally turning current_cpu_type() into
a function returning a constant.
o Use current_cpu_type() rather than direct access to struct cpuinfo_mips.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Cc: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5833/

MIPS: Hardwire detection of DSP ASE Rev 2 for systems, as required.

Most supported systems currently hardwire cpu_has_dsp to 0, so we also
can disable support for cpu_has_dsp2 resulting in a slightly smaller
kernel.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

MIPS: Move headfiles to new location below arch/mips/include

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>