Add a sysprop to configure number of retries polling for loop device

On some devices creating a loopback device might take more time (e.g.
due to memory pressure on device). This change adds a sysprop to make it
easier to configure on per-device basis the timeout for the loopback
device creation.

Bug: 237955261
Test: m
Test: device boots
Change-Id: I19ec94396be95f2457dd4446de11450c181245bc
2 files changed