libpayload: mips: Add macros to convert to/from KSEG{0,1} addresses

Add helper macros to convert between physical addresses and KSEG{0,1}
addresses.  Also get rid of the virt_to_{bus,phys}_offset variables
as these are fixed values.

As nobody seems to be using getpagesize() on MIPS, no need to keep
virtual.c.

BUG=chrome-os-partner:36258
BRANCH=none
TEST=Build and boot on Pistachio.

Change-Id: Ia26c8eae53eb8f860747a6b321363776841d1a94
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: c422b02e9a2a20d130913b1cfb835ad74c39ddca
Original-Change-Id: I9476cd225a08534830c700cba7bf9d3ef871757e
Original-Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
Original-Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/247190
Reviewed-on: http://review.coreboot.org/9821
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

payloads/libpayload/arch/mips/Makefile.inc

@@ -36,4 +36,3 @@ libc-y += sysinfo.c
 libc-y += string.c
 libc-y += timer.c
 libc-y += util.S
-libc-y += virtual.c