video: fbdev: ssd1307fb: Extract ssd1307fb_set_{col,page}_range()

Extract the code to set the column and page ranges into two helper
functions.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210727134730.3765898-4-geert@linux-m68k.org