time_init invokes timer64_init (which is __init annotation)
since all of these are invoked at init time, lets maintain
consistency by ensuring time_init is marked appropriately
as well.

This fixes the following warning with CONFIG_DEBUG_SECTION_MISMATCH=y

WARNING: vmlinux.o(.text+0x3bfc): Section mismatch in reference from the function time_init() to the function .init.text:timer64_init()
The function time_init() references
the function __init timer64_init().
This is often because time_init lacks a __init
annotation or the annotation of timer64_init is wrong.

Fixes: 546a3954 ("C6X: time management")
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Mark Salter <msalter@redhat.com>