ipq806x: Fix casting in cbmem_top() so >=2GB can be used

This explicitly casts CONFIG_SYS_SDRAM_BASE to an unsigned type so
we don't get compilation errors when increasing CONFIG_DRAM_SIZE_MB.

BUG=chrome-os-partner:29871
BRANCH=storm
TEST=compilation no longer fails with DRAM_SIZE set to 1024

Original-Signed-off-by: David Hendricks <dhendrix@chromium.org>
Original-Change-Id: I9717c39d87682d43ec4e7a4042d9b559a1d7eedb
Original-Reviewed-on: https://chromium-review.googlesource.com/206010
Original-Reviewed-by: Stefan Reinauer <reinauer@chromium.org>
(cherry picked from commit 178db896346ae8cbc5ddec5373a83688f32c62ba)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: I68c11d398820684ad928bdfdd74f7a6885247333
Reviewed-on: http://review.coreboot.org/8059
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Tested-by: build bot (Jenkins)
1 file changed