powerpc: remove leftover code of old GCC version checks

Clean up the leftover of commit f2910f0 ("powerpc: remove old
GCC version checks").

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/Makefile

@@ -422,10 +422,6 @@ else
 endif
 endif
 
-# Use the file '.tmp_gas_check' for binutils tests, as gas won't output
-# to stdout and these checks are run even on install targets.
-TOUT	:= .tmp_gas_check
-
 # Check toolchain versions:
 # - gcc-4.6 is the minimum kernel-wide version so nothing required.
 checkbin:
@@ -436,7 +432,3 @@ checkbin:
 		echo -n '*** Please use a different binutils version.' ; \
 		false ; \
 	fi
-
-
-CLEAN_FILES += $(TOUT)
-