board/ti/beagle/beagle.c: Fix build warnings

Fix:
beagle.c:257:13: warning: function declaration isn't a prototype
[-Wstrict-prototypes]
beagle.c:257:13: warning: function declaration isn't a prototype
[-Wstrict-prototypes]

Also make beagle_dvi_pup() checkpatch clean, fix:
ERROR: open brace '{' following function declarations go on the
next line

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