ar71xx: detect and enable MIPS DSP extensions, AR9344 supports them (fixes #11762)

SVN-Revision: 32520

target/linux/ar71xx/patches-3.3/630-MIPS-ath79-enable-dsp.patch

+--- a/arch/mips/include/asm/mach-ath79/cpu-feature-overrides.h
++++ b/arch/mips/include/asm/mach-ath79/cpu-feature-overrides.h
+@@ -42,7 +42,6 @@
+ #define cpu_has_mips64r1	0
+ #define cpu_has_mips64r2	0
+ 
+-#define cpu_has_dsp		0
+ #define cpu_has_mipsmt		0
+ 
+ #define cpu_has_64bits		0