ARM: omap2: remove incorrect __init annotation

ARM: omap2: remove incorrect __init annotation

omap3xxx_prm_enable_io_wakeup() is marked __init, but its caller is not, so
we get a warning with clang-8:

WARNING: vmlinux.o(.text+0x343c8): Section mismatch in reference from the function omap3xxx_prm_late_init() to the function .init.text:omap3xxx_prm_enable_io_wakeup()
The function omap3xxx_prm_late_init() references
the function __init omap3xxx_prm_enable_io_wakeup().
This is often because omap3xxx_prm_late_init lacks a __init
annotation or the annotation of omap3xxx_prm_enable_io_wakeup is wrong.

When building with gcc, omap3xxx_prm_enable_io_wakeup() is always
inlined, so we never noticed in the past.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Andrew Murray <andrew.murray@arm.com>
Signed-off-by: Olof Johansson <olof@lixom.net>