EDAC/skx_common: Remove redundant upper bound check for res->imc

EDAC/skx_common: Remove redundant upper bound check for res->imc

The following upper bound check for the memory controller physical index
decoded by ADXL is the only place where use the macro 'NUM_IMC' is used:

  res->imc > NUM_IMC - 1

Since this check is already covered by skx_get_mc_mapping(), meaning no
memory controller logical index exists for an invalid memory controller
physical index decoded by ADXL, remove the redundant upper bound check
so that the definition for 'NUM_IMC' can be cleaned up (in another patch).

Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20250731145534.2759334-6-qiuxu.zhuo@intel.com