zcache/zbud: Fix __init mismatch

We get:
WARNING: drivers/staging/zcache/zcache.o(.text+0x13a1): Section mismatch
in reference from the function zcache_init() to the function
.init.text:zbud_init()
The function zcache_init() references
the function __init zbud_init().
This is often because zcache_init lacks a __init
annotation or the annotation of zbud_init is wrong.

And this fixes it.

Acked-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>