EDAC/amd64: Fix size calculation for Non-Power-of-Two DIMMs

Each Chip-Select (CS) of a Unified Memory Controller (UMC) on AMD Zen-based
SOCs has an Address Mask and a Secondary Address Mask register associated with
it. The amd64_edac module logs DIMM sizes on a per-UMC per-CS granularity
during init using these two registers.

Currently, the module primarily considers only the Address Mask register for
computing DIMM sizes. The Secondary Address Mask register is only considered
for odd CS. Additionally, if it has been considered, the Address Mask register
is ignored altogether for that CS. For power-of-two DIMMs i.e. DIMMs whose
total capacity is a power of two (32GB, 64GB, etc), this is not an issue
since only the Address Mask register is used.

For non-power-of-two DIMMs i.e., DIMMs whose total capacity is not a power of
two (48GB, 96GB, etc), however, the Secondary Address Mask register is used
in conjunction with the Address Mask register. However, since the module only
considers either of the two registers for a CS, the size computed by the
module is incorrect. The Secondary Address Mask register is not considered for
even CS, and the Address Mask register is not considered for odd CS.

Introduce a new helper function so that both Address Mask and Secondary
Address Mask registers are considered, when valid, for computing DIMM sizes.
Furthermore, also rename some variables for greater clarity.

Fixes: 81f5090db843 ("EDAC/amd64: Support asymmetric dual-rank DIMMs")
Closes: https://lore.kernel.org/dbec22b6-00f2-498b-b70d-ab6f8a5ec87e@natrix.lt
Reported-by: Žilvinas Žaltiena <zilvinas@natrix.lt>
Signed-off-by: Avadhut Naik <avadhut.naik@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Yazen Ghannam <yazen.ghannam@amd.com>
Tested-by: Žilvinas Žaltiena <zilvinas@natrix.lt>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/20250529205013.403450-1-avadhut.naik@amd.com

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