[SPARC64]: fix section mismatch warning in pci_sunv4

Fix following warning:
WARNING: vmlinux.o(.text+0x3cf50): Section mismatch: reference to .init.text:page_in_phys_avail (between 'pci_sun4v_pbm_init' and 'sun4v_pci_init')

pci_sun4v_pbm_init and sun4v_pci_init was only used under __init
context so declare them _init.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>