platform/x86/amd/hsmp: Convert amd_hsmp_rdwr() to a function pointer

This is in preparation to ACPI, Non-ACPI split.
amd_hsmp_rdwr() is used to access HSMP protocol registers.
ACPI and Non-ACPI use different methods to access these registers.
Now that code is split and common functionality is kept in hsmp.c
we need to define a function pointer to handle these functions separately.

Signed-off-by: Suma Hegde <suma.hegde@amd.com>
Reviewed-by: Naveen Krishna Chatradhi <naveenkrishna.chatradhi@amd.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20241021111428.2676884-3-suma.hegde@amd.com


Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>