EDAC/skx_common: Allow decoding of SGX addresses

There are no "struct page" associations with SGX pages, causing the check
pfn_to_online_page() to fail. This results in the inability to decode the
SGX addresses and warning messages like:

  Invalid address 0x34cc9a98840 in IA32_MC17_ADDR

Add an additional check to allow the decoding of the error address and to
skip the warning message, if the error address is an SGX address.

Fixes: 1e92af09 ("EDAC/skx_common: Filter out the invalid address")
Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20240408120419.50234-1-qiuxu.zhuo@intel.com