CONFIG_NR_DRAM_BANKS: Remove unreferenced code as its always defined

CONFIG_NR_DRAM_BANKS: Remove unreferenced code as its always defined

Since commit 496892aefcbb ("configs: Migrate CONFIG_NR_DRAM_BANKS") &
commit dfc3221bdfd2 ("Kconfig: Migrate CONFIG_NR_DRAM_BANKS"),
CONFIG_NR_DRAM_BANKS is always defined with a value (4 is default).
It makes no sense to still carry code that is guarded with
"#ifndef CONFIG_NR_DRAM_BANKS" (and similar). This patch removes
all these unreferenced code paths.

Signed-off-by: Stefan Roese <sr@denx.de>
Reviewed-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>