seL4_libs: remove autoconf.h from seL4_libs

this commit removes autoconf.h generation from each lib and
append '#include <<lib_name>/gen_config.h>' after each
'#include <autoconf.h>' since autoconf.h is only the for the
kernel config now. This is a temporarily solution, since we
currently don't have a way to tell which header files each file
is trying to include when it includes 'autoconf.h'

trivial: Style libsel4platsupport/src/serial.c

Remove serial_objects_t

This interface won't scale to more complicated serial devices.
Instead drivers describe their requirements via calls to ps_io_ops and
the implementations of these interfaces can handle access and allocation
policies.

SELFOUR-1290: undo arbitrary config guard changes

RISC-V port

platsupport: s/ZF_LOGF/ZF_LOGE in serial init

This is not a fatal error: it's up to the app to decide that.

Fix all the whitespace

- remove trailing whitespace
- remove duplicate blank lines
- remove blank lines at end of files

Fix licenses

libsel4platsupport: add init_default_serial_caps

Uses a vka, vspace and simple interface to create platform specific
serial caps such as untyped caps, interrupt caps or ioport caps. This
functionality was moved here from sel4test for reuse in other
applications.

SELFOUR-862: CONFIG_PRINTING --> seL4_DebugPutChar

Use CONFIG_DEBUG_BUILD instead of SEL4_DEBUG_KERNEL

SEL4_DEBUG_KERNEL is a historic define from before CONFIG_DEBUG_BUILD existed
and is considered deprecated. With using a CONFIG_ variable this commit also
adds #include <autoconf.h> where neccessary

libsel4platsupport: Remove some unnecessary #includes, and add some missing ones.

libsel4platsupport: Remove unused __plat_serial_input_init_IRQ.