build: remove MIPS dsp/dsp2 CPU_SUBTYPE

There does not seem to be any meaningful difference in generated code.
This will save some time and space on snapshot builds

Signed-off-by: Felix Fietkau <nbd@nbd.name>

include/target.mk

@@ -172,8 +172,6 @@ ifeq ($(DUMP),1)
     CPU_CFLAGS_74kc = -mips32r2 -mtune=74kc
     CPU_CFLAGS_1004kc = -mips32r2 -mtune=1004kc
     CPU_CFLAGS_octeon = -march=octeon -mabi=64
-    CPU_CFLAGS_dsp = -mdsp
-    CPU_CFLAGS_dsp2 = -mdspr2
   endif
   ifeq ($(ARCH),i386)
     CPU_TYPE ?= i486