board/linkstation/ide.c: Fix GCC 4.6 build warnings

board/linkstation/ide.c: Fix GCC 4.6 build warnings

Fix:
ide.c: In function 'ide_preinit':
ide.c:69:21: warning: array subscript is above array bounds
[-Warray-bounds]
ide.c:69:21: warning: array subscript is above array bounds
[-Warray-bounds]
ide.c:70:17: warning: array subscript is above array bounds
[-Warray-bounds]

Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Reviewed-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>