Rename the fbdev mmap helper fb_pgprotect() to pgprot_framebuffer().
The helper sets VMA page-access flags for framebuffers in device I/O
memory.

Also clean up the helper's parameters and return value. Instead of
the VMA instance, pass the individial parameters separately: existing
page-access flags, the VMAs start and end addresses and the offset
in the underlying device memory rsp file. Return the new page-access
flags. These changes align pgprot_framebuffer() with other pgprot_()
functions.

v4:
	* fix commit message (Christophe)
v3:
	* rename fb_pgprotect() to pgprot_framebuffer() (Arnd)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> # m68k
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230922080636.26762-3-tzimmermann@suse.de

Move fbdev's file-I/O code into a separate file and contain it in
init and cleanup helpers. No functional changes.

v3:
	* add missing file fb_chrdev.c
v2:
	* rename source file (Sam)
	* include <linux/compat.h> (Javier, kernel test robot)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230613110953.24176-37-tzimmermann@suse.de