mx3fb: fix regression with uninitalized fb_info->mm_lock mutex

Remove call to the mx3fb_set_par() and the mx3fb_blank() before the
register_framebuffer().

This fixes a problem with uninitialized the fb_info->mm_lock mutex
introduced by the commit 537a1bf0 " fbdev: add mutex for fb_mmap
locking"

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>