bng_en: Add firmware communication mechanism

bng_en: Add firmware communication mechanism

Add support to communicate with the firmware.
Future patches will use these functions to send the
messages to the firmware.
Functions support allocating request/response buffers
to send a particular command. Each command has certain
timeout value to which the driver waits for response from
the firmware. In error case, commands may be either timed
out waiting on response from the firmware or may return
a specific error code.

Signed-off-by: Vikas Gupta <vikas.gupta@broadcom.com>
Reviewed-by: Bhargava Chenna Marreddy <bhargava.marreddy@broadcom.com>
Reviewed-by: Rajashekar Hudumula <rajashekar.hudumula@broadcom.com>
Link: https://patch.msgid.link/20250701143511.280702-4-vikas.gupta@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>