soc: qcom: dfc: Purge packets on flow delete

When a dedicated flow is deleted, the TX queue enable operation will
flush pending packets to the transport. This could cause unexpected
delay in processing packets on the default flow.

This change purges pending packets for a TX queue when a dedicated
bearer is deactivated.

CRs-fixed: 2469775
Change-Id: Idd5e0498f7a2d577d768188411161b79210263b2
Acked-by: Weiyi Chen <weiyic@qti.qualcomm.com>
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>