b43: Comment unused functions lpphy_restore_dig_flt_state and lpphy_disable_rx_gain_override

Commenting unused functions lpphy_restore_dig_flt_state and
lpphy_disable_rx_gain_override, may be we need these functions in future.

This also fixed following compilation warnings :
  CC [M]  drivers/net/wireless/b43/phy_lp.o
drivers/net/wireless/b43/phy_lp.c:383: warning: ‘lpphy_restore_dig_flt_state’ defined but not used
drivers/net/wireless/b43/phy_lp.c:891: warning: ‘lpphy_disable_rx_gain_override’ defined but not used

Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>