staging: wfx: apply naming rules in hif_tx_mib.c

All the functions of hif_tx_mib.c format data to be sent to the
hardware. In this file, the struct to be sent is always named 'arg'.

Also applies this rule to hif_set_macaddr().

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20210913130203.1903622-21-Jerome.Pouiller@silabs.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>