powerpc/kasan: Mark more real-mode code as not to be instrumented

powerpc/kasan: Mark more real-mode code as not to be instrumented

This marks more files and functions that can possibly be called in
real mode as not to be instrumented by KASAN.  Most were found by
inspection, except for get_pseries_errorlog() which was reported as
causing a crash in testing.

Reported-by: Nageswara R Sastry <rnsastry@linux.ibm.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/YoX1kZPnmUX4RZEK@cleo