arch: Rename fbdev header and source files

The per-architecture fbdev code has no dependencies on fbdev and can
be used for any video-related subsystem. Rename the files to 'video'.
Use video-sti.c on parisc as the source file depends on CONFIG_STI_CORE.

On arc, arm, arm64, sh, and um the asm header file is an empty wrapper
around the file in asm-generic. Let Kbuild generate the file. The build
system does this automatically. Only um needs to generate video.h
explicitly, so that it overrides the host architecture's header. The
latter would otherwise interfere with the build.

Further update all includes statements, include guards, and Makefiles.
Also update a few strings and comments to refer to video instead of
fbdev.

v3:
- arc, arm, arm64, sh: generate asm header via build system (Sam,
Helge, Arnd)
- um: rename fb.h to video.h
- fix typo in commit message (Sam)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Vineet Gupta <vgupta@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>