arch/arm/include/asm/arch-omap5/clocks.h: Fix GCC 4.2 warnings

Fix:
clocks.c: In function 'setup_post_dividers':
clocks.c:175: warning: comparison is always true due to limited range of
data type
clocks.c:177: warning: comparison is always true due to limited range of
data type
clocks.c:179: warning: comparison is always true due to limited range of
data type
clocks.c:181: warning: comparison is always true due to limited range of
data type
clocks.c:183: warning: comparison is always true due to limited range of
data type
clocks.c:185: warning: comparison is always true due to limited range of
data type
clocks.c:187: warning: comparison is always true due to limited range of
data type
clocks.c:189: warning: comparison is always true due to limited range of
data type

Signed-off-by: Anatolij Gustschin <agust@denx.de>
Cc: sricharan <r.sricharan@ti.com>
Cc: Tom Rini <trini@ti.com>