Provide MARCH_HAS_*_FEATURES defines which are supposed to be used
everywhere instead of the CONFIG_HAVE_MARCH_*_FEATURES defines.

Various header files contain code which depend on the
CONFIG_HAVE_MARCH_*_FEATURES defines, allowing for compile time
optimizations. If such code is used within the decompressor wrong code may
be generated (the compiler may generate instructions which are not
available for the minimum architecture level of the decompressor).

Therefore provide a new header file with MARCH_HAS_*_FEATURES defines,
which are only available if __DECOMPRESSOR is not defined. This way code
generation for the kernel image is still optimized depending on
CONFIG_HAVE_MARCH_*_FEATURES, while code generated for the decompressor is
compiled for the minimum architecture level.
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>