staging: sxg depends on X86

sxghif.h has code that explicitly will not build fo other architecures.
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/staging/sxg/Kconfig

 config SXG
 	tristate "Alacritech SLIC Technology Non-Accelerated 10Gbe support"
 	depends on PCI && NETDEV_10000
+	depends on X86
 	default n
 	help
 	  This driver supports the Alacritech SLIC Technology Non-Accelerated