staging: rtl8723bs: hal: odm_NoiseMonitor: Remove unused variable 'func_start'

staging: rtl8723bs: hal: odm_NoiseMonitor: Remove unused variable 'func_start'

Fixes the following W=1 kernel build warning(s):

 drivers/staging/rtl8723bs/hal/odm_NoiseMonitor.c: In function ‘odm_InbandNoise_Monitor_NSeries’:
 drivers/staging/rtl8723bs/hal/odm_NoiseMonitor.c:32:18: warning: variable ‘func_start’ set but not used [-Wunused-but-set-variable]

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Marco Cesati <marcocesati@gmail.com>
Cc: linux-staging@lists.linux.dev
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210414181129.1628598-53-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>