This patch fixes one infinite hang of bulk IN transfer in double buffer
case, the hang can be observed easily by test #6 of usbtest if musb is
configured as g_zero and fifo mode 3 is taken to enable double fifo.

In fact, the patch only removes the check for non-empty fifo before
loading data from new request into fifo since the check is not correct:

	-in double buffer case, fifo may accommodate more than one packet,
	even though it has contained one packet already and is non-empty

	-since last DMA is completed before calling musb_g_tx, it is sure
	that fifo may accommodate at least one packet

Without applying the patch, new requst enqueued from .complte may not
have a chance to be loaded into fifo, then will never be completed and
cause infinite hangs.

With the patch, on my beagle B5, test#6(queued bulk in) can be passed and
test result may go beyond 33Mbyte/s if musb is configured as g_zero and
fifo mode 3 is taken, follows the test command:

	#testusb -D DEV_NAME -c 1024 -t 6 -s 32768 -g 8   [1]

[1],
    -source of testusb : tools/usb/testusb.c under linux kernel;

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Acked-by: Anand Gadiyar <gadiyar@ti.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Cc: Anand Gadiyar <gadiyar@ti.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>