C6X: change main arch kbuild symbol

Currently the c6x architecture uses CONFIG_TMS320C6X as the main
architecture symbol. Most architectures use a more intuitive name
based on the architecture directory name. There are no current
users of TMS320C6X so this patch simply changes CONFIG_TMS320C6X
to the more intuitive CONFIG_C6X.
Signed-off-by: NMark Salter <msalter@redhat.com>
Acked-by: NMike Frysinger <vapier@gentoo.org>

arch/c6x/Kconfig

@@ -3,7 +3,7 @@
 # see Documentation/kbuild/kconfig-language.txt.
 #
 
-config TMS320C6X
+config C6X
 	def_bool y
 	select CLKDEV_LOOKUP
 	select GENERIC_IRQ_SHOW