staging: rtl8192e: rtl8192E_dev: remove unused variable

Fix the following gcc warning:

drivers/staging/rtl8192e/rtl8192e/r8192E_dev.c:693:15: warning: variable
‘tmpRegC’ set but not used [-Wunused-but-set-variable].

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Link: https://lore.kernel.org/r/1617767558-114050-1-git-send-email-jiapeng.chong@linux.alibaba.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>