staging: rtl8723bs: remove set but not used variable 'pszBBRegMpFile'

staging: rtl8723bs: remove set but not used variable 'pszBBRegMpFile'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/staging/rtl8723bs/hal/rtl8723b_phycfg.c: In function phy_BB8723b_Config_ParaFile:
drivers/staging/rtl8723bs/hal/rtl8723b_phycfg.c:436:77:
 warning: variable pszBBRegMpFile set but not used [-Wunused-but-set-variable]

It is never used so can be removed.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20190726140734.39564-1-yuehaibing@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>