MIPS: Netlogic: Add 32-bit support for XLP

Update asm/netlogic/haldefs.h to extend register access functions
nlm_{read,write}_reg64() for 32-bit compilation. When compiled for 32-bit
the functions will read 64 IO registers with interrupts disabled.

Signed-off-by: Jayachandran C <jchandra@broadcom.com>
Patchwork: http://patchwork.linux-mips.org/patch/5026/
Acked-by: John Crispin <blogic@openwrt.org>