RAS: ACPI: APEI: add conditional compilation to ARM error report functions

This prevents the unnecessary inclusion of ARM specific RAS error
handling routines in non-ARM platforms.

[mchehab: avoid unneeded ifdefs and fix coding style issues]
Signed-off-by: Daniel Ferguson <danielf@os.amperecomputing.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>