ARM: dts: msm: Set min-microvolt of pmxpoorwills_s1_level to RETENTION

pmxpoorwills_s1_level has resource as mss.lvl, which don't have the min svs
level.

Change-Id: Ic6a20c20af986727bb795dd6c7d79b89f7964ebf
Signed-off-by: Veera Vegivada <vvegivad@codeaurora.org>