msm: 8960: add flag to invert soft reset gpio

There is an inverter in the gpio connection so that pulling
the soft reset gpio HIGH in fact pulls the PS_HOLD of the
external modem LOW. The flag is already supported in the
mdm driver but was not set in the platform data.

Change-Id: I5632fde7e70328f3c6530b24f14ef2127cce56be
Signed-off-by: Joel King <joelking@codeaurora.org>