slim-msm-ngd: Fix unbalanced core irq disable from ndg_slim_enable

The 'commit 5adc2a6e ("slim-msm-ngd: Disable core irq
in SSR/PDR Down notification")' added irq_enable and disable from
ngd_slim_enable function. irq will be enabled only if msm_slim_qmi_init
success where as disabled by default in else block. If QMI init is
failed we will disable the IRQ twice during SSR testing.

As the interrupt line is not enabled, capability exchange is timing out and
leading to freed memory access inside ngd_xfer_msg.

Move irq enable in ndg_slim_enable without depending on QMI init.

Change-Id: Id32b0d283b1653bb4085231694031b0df126cf4b
Signed-off-by: Chandana Kishori Chiluveru <cchiluve@codeaurora.org>