EDAC/xgene: Fix deferred probing

The driver overrides error codes returned by platform_get_irq_optional()
to -EINVAL for some strange reason, so if it returns -EPROBE_DEFER, the
driver will fail the probe permanently instead of the deferred probing.
Switch to propagating the proper error codes to platform driver code
upwards.

  [ bp: Massage commit message. ]

Fixes: 0d442930

 ("EDAC: Add APM X-Gene SoC EDAC driver")
Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20220124185503.6720-3-s.shtylyov@omp.ru