iwlwifi: rename ACPI_SAR_NUM_CHAIN_LIMITS to ACPI_SAR_NUM_CHAINS

The "LIMITS" in the macro name don't have much meaning, so remove it
to make the macro shorter and better reflect that this is the number
of chains that we have limits for.

Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210805130823.65591c9fa2af.Ie7e4ba94c903ef444cb07df61891394c11c7c864@changeid
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>