msm: mdm: Assert soft_reset_gpio in mdm_power_down_common

In cases where the external modem is powered up very early in the
boot up process, user space application is not loaded as a result
mdm2ap_status is never pulled high. In case where we need to shutdown
the phone for charging we leave the ap2mdm_soft_reset_gpio pulled
high which results in leakage. Assert the ap2mdm_soft-reset_gpio
irrespective of the state of mdm2ap_status gpio.

CRs-Fixed: 425684
Change-Id: Icd37ac8eec1a8b9259563f2627ee57340f4e9f59
Signed-off-by: Taniya Das <tdas@codeaurora.org>