mtd/cmdlinepart.c: remove static declaration of mtdpart_setup

Revert the following commit :

commit ddacff1f20fc5c96cc73e2975258e05d298c97cc
Author: Adrian Bunk <bunk@stusta.de>
Date:   Sat Nov 25 20:15:41 2006 +0100

    [MTD] make drivers/mtd/cmdlinepart.c:mtdpart_setup() static

    This patch makes the needlessly global mtdpart_setup() static.

    Signed-off-by: Adrian Bunk <bunk@stusta.de>
    Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Otherwise, the omap-hw can't work when the partition layout is in a TAG.