of: replace Asahi Kasei Corp vendor prefix

Current vendor-prefixes.txt already has "ak" prefix for Asahi Kasei Corp
by ae8c420(of: Add vendor prefix for Asahi Kasei Corp.)

It went through the appropriate review process. But, almost all
Asahi Kasei chip drivers are using "asahi-kasei" prefix today.
(arch/arm/boot/dts/tegra20-seaboard.dts only is using "ak,ak8975",
 but there are instances of "asahi-kasei,ak8975" in other dts files.
 And drivers/iio/magnetometer/ak8975.c doesn't support "ak,ak8975" prefix)
So, we made a mistake there.

In addition, checkpatch.pl reports WARNING if it is using "asahi-kasei"
prerfix in DT file.
(DT compatible string vendor "asahi-kasei" appears un-documented)

Marking it deprecated and warning with checkpatch is certainly
preferable. So, this patch replace "ak" to "asahi-kasei" in
vendor-prefixes.txt. (and fixup tegra20-seaboard)

OTOH, Asahi Kasei is usually referred to as "AKM", but this patch
doesn't care about it. Because no DT is using that today.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Acked-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/vendor-prefixes.txt

@@ -9,7 +9,6 @@ ad	Avionic Design GmbH
 adapteva	Adapteva, Inc.
 adi	Analog Devices, Inc.
 aeroflexgaisler	Aeroflex Gaisler AB
-ak	Asahi Kasei Corp.
 allwinner	Allwinner Technology Co., Ltd.
 altr	Altera Corp.
 amcc	Applied Micro Circuits Corporation (APM, formally AMCC)
@@ -20,6 +19,7 @@ amstaos	AMS-Taos Inc.
 apm	Applied Micro Circuits Corporation (APM)
 arm	ARM Ltd.
 armadeus	ARMadeus Systems SARL
+asahi-kasei	Asahi Kasei Corp.
 atmel	Atmel Corporation
 auo	AU Optronics Corporation
 avago	Avago Technologies

arch/arm/boot/dts/tegra20-seaboard.dts

@@ -406,7 +406,7 @@
 		clock-frequency = <400000>;
 
 		magnetometer@c {
-			compatible = "ak,ak8975";
+			compatible = "asahi-kasei,ak8975";
 			reg = <0xc>;
 			interrupt-parent = <&gpio>;
 			interrupts = <TEGRA_GPIO(N, 5) IRQ_TYPE_LEVEL_HIGH>;