powerpc/xmon: replace sizeof calculations with ARRAY_SIZE macro

powerpc/xmon: replace sizeof calculations with ARRAY_SIZE macro

The calculations for operand/opcode/macro numbers are done in an
identical manner to the already existing ARRAY_SIZE macro in
linux/array_size.h

This patch replaces the sizeof calculations with the macro to make the
code cleaner and more immediately obvious what it is doing.

Signed-off-by: Ruben Wauters <rubenru09@aol.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20250719225225.2132-2-rubenru09@aol.com