ARM: keystone2: Refactor MSMC macros to avoid #ifdeffery

MSMC segment Privilege ID is not consistent accross the keystone2 SoCs.
As the first step to ensure complete SoC wide coherency setup, lets
refactor the macros to remove the #if-deffery around the code which
obfuscates which IDs are actually enabled for which SoC.

As a result of this change the PCIe configuration is moved after the
msmc configuration is complete, but that should ideally have no
functional impact.

Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>