powerpc/fsl-booke: Rename b4qds.dts -> b4qds.dtsi.

powerpc/fsl-booke: Rename b4qds.dts -> b4qds.dtsi.

This file is a common include for B4860 and B4420 but is not a valid DTS itself:
	  DTC     arch/powerpc/boot/b4qds.dtb
	Error: arch/powerpc/boot/dts/b4qds.dts:35.1-2 syntax error
	FATAL ERROR: Unable to parse input tree
	make[1]: *** [arch/powerpc/boot/b4qds.dtb] Error 1
	make: *** [b4qds.dtb] Error 2

I spotted in build tests of device-tree.git, announcement
https://lkml.org/lkml/2013/4/24/209, which builds *.dts. Probably no one would
do this this in real life on linux.git but it still seems worth fixing.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Cc: Shaveta Leekha <shaveta@freescale.com>
Cc: Minghuan Lian <Minghuan.Lian@freescale.com>
Cc: Andy Fleming <afleming@freescale.com>
Cc: Poonam Aggrwal <poonam.aggrwal@freescale.com>
Cc: Ramneek Mehresh <ramneek.mehresh@freescale.com>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Scott Wood <scottwood@freescale.com>