board/esd/cpci750/sdram_init.c: Fix GCC 4.6 build warnings

Fix:
sdram_init.c: In function 'check_dimm':
sdram_init.c:267:50: warning: variable 'trrd_clocks' set but not used
[-Wunused-but-set-variable]
sdram_init.c:267:37: warning: variable 'tras_clocks' set but not used
[-Wunused-but-set-variable]
sdram_init.c:267:24: warning: variable 'trcd_clocks' set but not used
[-Wunused-but-set-variable]
sdram_init.c:267:8: warning: variable 'trp_clocks' set but not used
[-Wunused-but-set-variable]
sdram_init.c:253:16: warning: variable 'spd_checksum' set but not used
[-Wunused-but-set-variable]
sdram_init.c: In function 'initdram':
sdram_init.c:1693:14: warning: variable 's1' set but not used
[-Wunused-but-set-variable]
sdram_init.c:1693:6: warning: variable 's0' set but not used
[-Wunused-but-set-variable]

Biggest part o the fix is converting the custom debug code to standard
debug().

No attempts were made to cleanup the code.

Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Reinhard Arlt <reinhard.arlt@esd-electronics.com>