staging: r8188eu: Fix smatch warnings for hal/rtl8188e_phycfg.c

Smatch reports the following:
drivers/staging/rtl8188eu/hal/rtl8188e_phycfg.c:857 getTxPowerIndex88E() error: buffer overflow 'pHalData->BW20_24G_Diff' 2 <= 2
drivers/staging/rtl8188eu/hal/rtl8188e_phycfg.c:864 getTxPowerIndex88E() error: buffer overflow 'pHalData->BW20_24G_Diff' 2 <= 2

The array in question is large enough to handle RADIO_PATH_X, where X is A or B.
The lines in question refer to RADIO_PATH_C, which is defined as 2.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>