USB: ci13xxx_msm_hsic: Mark ignore_children for Runtime PM handling

HSIC UDC driver manages runtime PM on its own and doesn't expect
its children to use any runtime PM APIs. Mark ignore_children
flag for the same so that PM core ignores children of this device.
This can otherwise cause HSIC not to enter LPM due to non-zero
PM usage_count which is incremented only on runtime_resume but
has to be decremented explicitly. While at it also replace
pm_runtime_get_sync with pm_runtime_resume call on CONNECT
notification for the very reason that driver expects only
runtime_resume API to make usage_count from 0 to 1 and
pm_runtime_put_noidle ensures it never becomes -1.

Change-Id: I07190aa1460910dd0ec8d3883b29b160a88d1d32
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>