staging: r8188eu: set path a explicitly

We've already limited the rtw_wx_write_rf function to RF_PATH_A in commit
3b011b09 ("staging: r8188eu: limit rf register writes to path a").

Set RF_PATH_A explicitly when we call rtl8188e_PHY_SetRFReg. This will
make it easier later to verify that all callers of rtl8188e_PHY_SetRFReg
use path a.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220212161737.381841-2-martin@kaiser.cx


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