usb: f_gsi: Avoid gsi ep operations if run/stop is cleared

The GSI operations for GSI_EP_OP_PREPARE_TRBS and GSI_EP_OP_STARTXFER
should not proceed if run/stop is cleared. Since ipa_work_handler runs
in worqueue context there might be a race between run/stop STARTXFER
and ENDXFER which can lead to SMMU fault. This change add checks to
avoid gsi ep operations when run/stop is cleared.

Change-Id: I9f64dee7020aec9cccfde8d247c0b53d9cc1f234
Signed-off-by: Pratham Pratap <prathampratap@codeaurora.org>