soc: qcom: dfc: Fix potential data stall

The worker thread callback can potentially fail to acquire
the trylock(). In such a case, retry to acquire the lock to avoid
dropping any flow enable messages which would result in a stall.

Usually multiple flow control messages with flow enable are sent
so this scenario could likely never occur.

CRs-Fixed: 2285862
Change-Id: Ic92d811c65e48829bcad26f3b8b6b720d16c6c1e
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>