drm/ssd130x: Fix pitch calculation in ssd130x_fb_blit_rect()

The page height must be taken into account only for vertical coordinates
and heights, not for horizontal coordinates and widths.

Fixes: 179a790a ("drm/ssd130x: Set the page height value in the device info data")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/54deec2ec533e90544faa8c60a0c2518c58f3e9c.1689252746.git.geert@linux-m68k.org