wifi: iwlwifi: pcie: Move txcmd size/align calculation to callers

Refactor iwl_trans_init to accept txcmd_size and txcmd_align as parameters
instead of calculating them internally.

Signed-off-by: Yedidya Benshimol <yedidya.ben.shimol@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250709081300.237285d81461.I3552860dd062a523606c8a5c85c9a6f0d4f04262@changeid