ARM: dts: at91: at91sam9g25: fix mux-mask pinctrl property

There are only 19 PIOB pins having primary names PB0-PB18. Not all of them
have a 'C' function. So the pinctrl property mask ends up being the same as the
other SoC of the at91sam9x5 series.
Reported-by: Marek Sieranski <marek.sieranski@microchip.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: <stable@vger.kernel.org> # v3.8+
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

arch/arm/boot/dts/at91sam9g25.dtsi

@@ -21,7 +21,7 @@ pinctrl@fffff400 {
 				atmel,mux-mask = <
 				      /*    A         B          C     */
 				       0xffffffff 0xffe0399f 0xc000001c  /* pioA */
-				       0x0007ffff 0x8000fe3f 0x00000000  /* pioB */
+				       0x0007ffff 0x00047e3f 0x00000000  /* pioB */
 				       0x80000000 0x07c0ffff 0xb83fffff  /* pioC */
 				       0x003fffff 0x003f8000 0x00000000  /* pioD */
 				      >;