[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/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 0c45855..823a8cb 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -34,6 +34,8 @@
 
 	/* Text and gots */
 	.text : {
+		ALIGN_FUNCTION();
+		*(.text.head)
 		_text = .;
 		TEXT_TEXT
 		SCHED_TEXT