board/apollon/apollon.c: Fix GCc 4.6 build warnings.

Fix:
apollon.c: In function 'dram_init':
apollon.c:188:29: warning: variable 'cpu' set but not used
[-Wunused-but-set-variable]
apollon.c:188:20: warning: variable 'rev' set but not used
[-Wunused-but-set-variable]
apollon.c:187:26: warning: variable 'size1' set but not used
[-Wunused-but-set-variable]

Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Kyungmin Park <kyungmin.park@samsung.com>