powerpc/boot: Don't always pass -mcpu=powerpc when building 32-bit uImage

commit ff7c76f66d upstream.

When CONFIG_TARGET_CPU is specified then pass its value to the compiler
-mcpu option. This fixes following build error when building kernel with
powerpc e500 SPE capable cross compilers:

    BOOTAS  arch/powerpc/boot/crt0.o
  powerpc-linux-gnuspe-gcc: error: unrecognized argument in option ‘-mcpu=powerpc’
  powerpc-linux-gnuspe-gcc: note: valid arguments to ‘-mcpu=’ are: 8540 8548 native
  make[1]: *** [arch/powerpc/boot/Makefile:231: arch/powerpc/boot/crt0.o] Error 1

Similar change was already introduced for the main powerpc Makefile in
commit 446cda1b21 ("powerpc/32: Don't always pass -mcpu=powerpc to the
compiler").

Fixes: 40a75584e5 ("powerpc/boot: Build wrapper for an appropriate CPU")
Cc: stable@vger.kernel.org # v5.19+
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/2ae3ae5887babfdacc34435bff0944b3f336100a.1674632329.git.christophe.leroy@csgroup.eu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/powerpc/boot/Makefile

@@ -39,13 +39,19 @@ BOOTCFLAGS    := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
 		 $(LINUXINCLUDE)
 
 ifdef CONFIG_PPC64_BOOT_WRAPPER
-ifdef CONFIG_CPU_LITTLE_ENDIAN
-BOOTCFLAGS	+= -m64 -mcpu=powerpc64le
+BOOTCFLAGS	+= -m64
 else
-BOOTCFLAGS	+= -m64 -mcpu=powerpc64
+BOOTCFLAGS	+= -m32
 endif
+
+ifdef CONFIG_TARGET_CPU_BOOL
+BOOTCFLAGS	+= -mcpu=$(CONFIG_TARGET_CPU)
+else ifdef CONFIG_PPC64_BOOT_WRAPPER
+ifdef CONFIG_CPU_LITTLE_ENDIAN
+BOOTCFLAGS	+= -mcpu=powerpc64le
 else
-BOOTCFLAGS	+= -m32 -mcpu=powerpc
+BOOTCFLAGS	+= -mcpu=powerpc64
+endif
 endif
 
 BOOTCFLAGS	+= -isystem $(shell $(BOOTCC) -print-file-name=include)