staging: rtl8723bs: Remove set but not used variable 'oldcnt'

staging: rtl8723bs: Remove set but not used variable 'oldcnt'

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

drivers/staging/rtl8723bs/hal/sdio_ops.c: In function sdio_read_port:
drivers/staging/rtl8723bs/hal/sdio_ops.c:430:6: warning: variable oldcnt set but not used [-Wunused-but-set-variable]

It is not used since commit dedf215bd1c7 ("staging:
rtl8723bs: remove unused code")

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Link: https://lore.kernel.org/r/1570354382-86879-1-git-send-email-zhengbin13@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>