[POWERPC] Fix modpost warnings from head*.S on ppc32

We get warnings like the following from the various ppc32 head*.S files:

WARNING: vmlinux.o(.text+0x358): Section mismatch: reference to .init.text:early_init (between 'skpinv' and 'interrupt_base')
WARNING: vmlinux.o(.text+0x380): Section mismatch: reference to .init.text:machine_init (between 'skpinv' and 'interrupt_base')
WARNING: vmlinux.o(.text+0x384): Section mismatch: reference to .init.text:MMU_init (between 'skpinv' and 'interrupt_base')
WARNING: vmlinux.o(.text+0x3aa): Section mismatch: reference to .init.text:start_kernel (between 'skpinv' and 'interrupt_base')
WARNING: vmlinux.o(.text+0x3ae): Section mismatch: reference to .init.text:start_kernel (between 'skpinv' and 'interrupt_base')

Added a .text.head section simliar to what other architectures do since
modpost already excludes this from its warnings.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/include/asm-powerpc/ppc_asm.h b/include/asm-powerpc/ppc_asm.h
index 211fdae..2dbd4e7 100644
--- a/include/asm-powerpc/ppc_asm.h
+++ b/include/asm-powerpc/ppc_asm.h
@@ -209,6 +209,10 @@
 
 #else /* 32-bit */
 
+#define _ENTRY(n)	\
+	.globl n;	\
+n:
+
 #define _GLOBAL(n)	\
 	.text;		\
 	.stabs __stringify(n:F-1),N_FUN,0,0,n;\