wifi: iwlwifi: uefi: open code the PPAG table store operation

wifi: iwlwifi: uefi: open code the PPAG table store operation

The structure in firmware runtime will need to grow because we're adding
a subband for UNII-9.
This means that we will soon no longer be able to just memcpy the data
from the UEFI table. The layout of the array will change.
Tediously copy the data byte-byte to make sure things get to the right
place even when we'll increase the number of subbands.
Make it easier for the uefi_cnv_var_ppag structure to grow by
simpiflying the layout it becomes an array of s8.
The layout of the structure becomes less obvious from the structure's
declaration, but then the code is more flexible.

Don't use UEFI_SAR_MAX_SUB_BANDS_NUM for the number of bands for PPAG.
Of course, SAR related structures will grow in future patches, but
decouple SAR and PPAG to make the work easier.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20260319110722.61e729ea2bde.I9d9cda29f576290bf966f780bf7ad5af34970e6f@changeid