msm: qpnp-power-on: Enable reset on long press of PWR key

Commit d2111860-"platform:
qpnp-power-on: choose correct s2 control registers" inadvertently
overwrote the KPDPWR S2 Control2 register disabling the S2 reset,
as a result of which long press of power key did not make the device
to go into download mode.

This change fixes the situation by explicitly adding the dt property
"qcom,support-reset" in the KPDPWR child node of PON module. This
enables s2 reset as well as configures the s1 and s2 timers for KPDPWR
reset source. Now long press of power key makes the device to go into
download mode.

CRs-Fixed: 673974
Change-Id: I4118ba9963f287c4ca88b6ea61322907321e1e16
Signed-off-by: Abinaya P <abinayap@codeaurora.org>