wifi: wcn36xx: Move firmware feature bit storage to dedicated firmware.c file

The naming of the get/set/clear firmware feature capability bits doesn't
really follow the established namespace pattern of
wcn36xx_logicalblock_do_something();

The feature bits are accessed by smd.c and main.c. It would be nice to
display the found feature bits in debugfs. To do so though we should tidy
up the namespace a bit.

Move the firmware feature exchange API to its own file - firmware.c giving
us the opportunity to functionally decompose other firmware related
accessors as appropriate in future.

Reviewed-by: Loic Poulain <loic.poulain@linaro.org>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20220727161655.2286867-3-bryan.odonoghue@linaro.org