msm: mdss: xlog: fix issue preventing dump address to be stored

Fix bug in xlog dump which prevents the virtual address
of the registers to be stored in the driver context.

Change-Id: I15fba4b8f88b31b8cd9eb27a21548e04a9a286ff
Signed-off-by: Ingrid Gallardo <ingridg@codeaurora.org>