staging: r8188eu: remove HW_VAR_H2C_FW_PWRMODE

Remove the HW_VAR_H2C_FW_PWRMODE case from SetHwReg8188EU() and move
its functionality to a new function in rtw_pwrctrl.c. This is part of
the ongoing effort to get rid of the unwanted hal layer.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20220409120627.10633-5-straube.linux@gmail.com


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