memory: emif: remove set but not used variables 'cs1_used' and 'custom_configs'

drivers/memory/emif.c:1616:9: warning:
 variable cs1_used set but not used [-Wunused-but-set-variable]
drivers/memory/emif.c:1624:36: warning:
 variable custom_configs set but not used [-Wunused-but-set-variable]

They are never used since introduction.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>