platform/x86: intel_pmc_ipc: fix gcr offset

According to Broxton APL spec, PMC MIMO resources for Global Control
Registers(GCR) are located at 4K(0x1000) offset from IPC base address.
In this driver, PLAT_RESOURCE_GCR_OFFSET macro defines the offset of GCR
region base address from IPC base address and its current value of
0x1008 is incorrect because it points to location for PMC_CFG register
and not the GCR base address itself.

GCR Base = IPC1 Base + 0x1000.

This patch fixes this offset issue.

Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>