Instead of having one common FDT MPXY RPMI mailbox client drivers
for various RPMI service groups, split this driver into two parts:
1) Common MPXY RPMI mailbox client library
2) MPXY driver for RPMI clock service group
The above split enables having a separate MPXY driver for each
RPMI clock service group and #1 (above) will allow code sharing
between various MPXY RPMI drivers.
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
