ARM: dts: msm: set ibb discharge resistor to 300k for PMI8996

PMI8996 has a 1.5nF reference capacitor which requires a 300k
discharge resistance. Set the qcom,qpnp-ibb-discharge-resistor
property to 300 for all devices that use PMI8996.

While we are here, clean up the ibb discharge resistance values
for devices that use PMI8994 and PMI8950 since they all use the
same reference capacitance.

CRs-Fixed: 908873
Change-Id: Icd4593f684d3b06561ac638305b270186258eb42
Signed-off-by: Nicholas Troast <ntroast@codeaurora.org>