add DRAM controller register header and fix printf issue

[YuzukiTsuru]

• add arch/arm32/mach-t113s3/reg-dram.h for DRAM controller register
• Fix auto_scan_dram_size using wrong reg #16
• add some comment for dram driver

Test LOG:

[I] AWBoot r25 starting...
[D] DRAM BOOT DRIVE INFO: V0.24
[D] DRAM CLK = 792 MHz
[D] DRAM Type = 3 (2:DDR2,3:DDR3)
[D] DRAMC read ODT off
[D] ZQ value = 0x12f
[D] DDR efuse: 0xa
[D] single rank and full DQ
[D] DDR efuse: 0xa
[D] rank 0 row = 13
[D] rank 0 bank = 8
[D] rank 0 page size = 2 KB
[D] DRAM ODT value: 0x42
[D] DDR efuse: 0xa
[D] DRAM: size = 128MB
[D] DRAM: simple test OK
[T] SMHC: set clock to 400.00KHz