Input: parkbd - drop bogus __init from parkbd_allocate_serio()

WARNING: vmlinux.o(.text+0x1056606): Section mismatch in reference from the function parkbd_attach() to the function .init.text:parkbd_allocate_serio()
The function parkbd_attach() references
the function __init parkbd_allocate_serio().
This is often because parkbd_attach lacks a __init
annotation or the annotation of parkbd_allocate_serio is wrong.

Commit 33ca8ab9 ("Input: parkbd - use parallel port device
model") dropped the __init attribute from the sole caller of
parkbd_allocate_serio(), but forgot to remove it from
parkbd_allocate_serio() itself.

Fixes: 33ca8ab9 ("Input: parkbd - use parallel port device model")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>