mfd: twl-core: Fix section annotations on {,un}protect_pm_master

When building the kernel with Clang, the following section mismatch
warning appears:

WARNING: vmlinux.o(.text+0x3d84a3b): Section mismatch in reference from
the function twl_probe() to the function
.init.text:unprotect_pm_master()
The function twl_probe() references
the function __init unprotect_pm_master().
This is often because twl_probe lacks a __init
annotation or the annotation of unprotect_pm_master is wrong.

Remove the __init annotation on the *protect_pm_master functions so
there is no more mismatch.

Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>