serial: msm_geni_serial: Initialize 'ret' with zero

Initialize the local variable 'ret' with zero to
prevent un-initialized access. Also fix uninitialized
uport pointers access from msm_geni_serial_probe().

Change-Id: I25198737992f24f7b06e77e68f29ba3263fb0b30
Signed-off-by: Chandana Kishori Chiluveru <cchiluve@codeaurora.org>