parisc: Fix fall-through warnings in fpudispatch.c

In fpudispatch.c we see a lot of fall-through warnings, but for this file we
prefer to not mark the switches and instead keep it in it's original state as
it's copied from HP-UX.

Fixes: a035d552 ("Makefile: Globally enable fall-through warning")
Signed-off-by: Helge Deller <deller@gmx.de>

arch/parisc/math-emu/Makefile

@@ -18,3 +18,4 @@ obj-y	 := frnd.o driver.o decode_exc.o fpudispatch.o denormal.o \
 # other very old or stripped-down PA-RISC CPUs -- not currently supported
 
 obj-$(CONFIG_MATH_EMULATION)	+= unimplemented-math-emulation.o
+CFLAGS_REMOVE_fpudispatch.o	= -Wimplicit-fallthrough=3