[POWERPC] vdso_do_func_patch{32,64}() must be __init

This fixes the following section mismatches:

<--  snip  -->

...
WARNING: vmlinux.o(.text+0xe49c): Section mismatch in reference from the function .vdso_do_func_patch64() to the function .init.text:.find_symbol64()
WARNING: vmlinux.o(.text+0xe4d0): Section mismatch in reference from the function .vdso_do_func_patch64() to the function .init.text:.find_symbol64()
WARNING: vmlinux.o(.text+0xe56c): Section mismatch in reference from the function .vdso_do_func_patch32() to the function .init.text:.find_symbol32()
WARNING: vmlinux.o(.text+0xe5a0): Section mismatch in reference from the function .vdso_do_func_patch32() to the function .init.text:.find_symbol32()
...

<--  snip  -->

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>