[xburst] udc: Fix recursive spinlocks

Driver had recursive spinlock locking: 1. jz4740_queue() acquires lock 2. done()
is called in chain:
jz4740_queue()->jz4740_ep0_kick()->jz4740_ep0_in()->write_fifo_ep0()->done() and
it tries to acquire same lock. 3. Deadlock.

Signed-off-by:
Yauhen Kharuzhy <jekhor@gmail.com>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@21619 3c298f89-4303-0410-b956-a3cf2f4a3e73