fbdev: sh_mipi_dsi: fix a section mismatch

sh_mipi_setup() is called from a .text function, therefore it cannot be
__init. Additionally, sh_mipi_remove() can be moved to the .devexit.text
section.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>