mailbox: pcc: Don't access an unmapped memory address space

The acpi_pcc_probe() may end up accessing memory outside of the PCCT
table space causing the kernel panic(). Increment the pcct_entry
pointer after parsing 'HW-reduced Communications Subspace' to fix
the problem. This change also enables the parsing of subtable at
index 0.

Signed-off-by: Shanker Donthineni <shankerd@codeaurora.org>
Acked-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>