ACPI: PPTT: Remove acpi_find_cache_levels()

acpi_find_cache_levels() is used at a single place and is short
enough to be merged into the calling function. The removal allows
an easier renaming of the calling function in the next patch.

Also reorder the local variables in the 'reversed Christmas tree'
order.

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Jeremy Linton <jeremy.linton@arm.com>