PCIe AER: prevent AER injection if hardware masks error reporting

The Correcteable/Uncorrectable Error Mask Registers are used by PCIe AER
driver which will controls the reporting of individual errors to PCIe RC
via PCIe error messages.

If hardware masks special error reporting to RC, the aer_inject driver
should not inject aer error.

Acked-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Youquan, Song <youquan.song@intel.com>
Acked-by: Ying, Huang <ying.huang@intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>