staging: rtlwifi: rtl8822be: Remove set but not used variable 'curtxbw_40mhz'
Fixes gcc '-Wunused-but-set-variable' warning:
drivers/staging/rtlwifi/rtl8822be/hw.c: In function 'rtl8822be_update_hal_rate_mask':
drivers/staging/rtlwifi/rtl8822be/hw.c:2144:5: warning:
variable 'curtxbw_40mhz' set but not used [-Wunused-but-set-variable]