power: qpnp-fg: fix offset SRAM reads

Fix a bug in the fg_mem_read function which did not
correctly read starting at a given offset.

After an offset read commences one needs to re-configure
the address prior to doing an aligned read.

Change-Id: I4dc3c07bdfbdf17110e988b99519be0b6881d13f
Signed-off-by: David Keitel <dkeitel@codeaurora.org>