[U-Boot] unused-const-variable warnings in FSL DDR driver

Hi York,

When compiling latest u-boot with gcc 6.3 compiler, I get several 'unused-const-variable' warnings in options.c file of FSL DDR driver. Affected variables are for (DIMM_SLOTS_PER_CTLR==2) configuration (e.g. dual_0S[4]) and warnings could be fixed with the patch applied.

What do you think?

Best regards, Thomas