mmc: alcor: remove set but not used variables 'len, clock_out'

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

drivers/mmc/host/alcor.c: In function 'alcor_data_set_dma':
drivers/mmc/host/alcor.c:124:12: warning:
 variable 'len' set but not used [-Wunused-but-set-variable]

drivers/mmc/host/alcor.c:648:15: warning:
 variable 'clock_out' set but not used [-Wunused-but-set-variable]

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Oleksij Rempel <linux@rempel-privat.de>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>