powerpc/boot: Clean up Makefile after cflags and asflags separation

Tidy pass over boot Makefile. Move variables together where possible.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230606064657.183969-5-npiggin@gmail.com

arch/powerpc/boot/Makefile

@@ -32,14 +32,6 @@ else
     BOOTAR := $(AR)
 endif
 
-BOOTCPPFLAGS	:= -nostdinc $(LINUXINCLUDE)
-BOOTCPPFLAGS	+= -isystem $(shell $(BOOTCC) -print-file-name=include)
-
-BOOTCFLAGS    := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
-		 -fno-strict-aliasing -O2 -msoft-float -mno-altivec -mno-vsx \
-		 $(call cc-option,-mno-spe) $(call cc-option,-mspe=no) \
-		 -pipe -fomit-frame-pointer -fno-builtin -fPIC
-
 ifdef CONFIG_PPC64_BOOT_WRAPPER
 BOOTTARGETFLAGS	+= -m64
 BOOTTARGETFLAGS	+= -mabi=elfv2
@@ -76,15 +68,22 @@ else
 BOOTTARGETFLAGS	+= -mlittle-endian
 endif
 
-BOOTAFLAGS	:= -D__ASSEMBLY__ $(BOOTTARGETFLAGS) -pipe
-
-BOOTARFLAGS	:= -crD
+BOOTCPPFLAGS	:= -nostdinc $(LINUXINCLUDE)
+BOOTCPPFLAGS	+= -isystem $(shell $(BOOTCC) -print-file-name=include)
 
-BOOTCFLAGS	+= $(call cc-option,-mno-prefixed) \
+BOOTCFLAGS	:= -pipe $(BOOTTARGETFLAGS) \
+		   -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
+		   -fno-strict-aliasing -O2 \
+		   -msoft-float -mno-altivec -mno-vsx \
+		   $(call cc-option,-mno-prefixed) \
 		   $(call cc-option,-mno-pcrel) \
-		   $(call cc-option,-mno-mma)
+		   $(call cc-option,-mno-mma) \
+		   $(call cc-option,-mno-spe) $(call cc-option,-mspe=no) \
+		   -fomit-frame-pointer -fno-builtin -fPIC
+
+BOOTAFLAGS	:= -pipe $(BOOTTARGETFLAGS) -D__ASSEMBLY__
 
-BOOTCFLAGS	+= $(BOOTTARGETFLAGS)
+BOOTARFLAGS	:= -crD
 
 ifdef CONFIG_CC_IS_CLANG
 BOOTCFLAGS += $(CLANG_FLAGS)