i2c: i2c-tiny-usb: fix buffer not being DMA capable

Since v4.9 i2c-tiny-usb generates the below call trace
and longer works, since it can't communicate with the
USB device. The reason is, that since v4.9 the USB
stack checks, that the buffer it should transfer is DMA
capable. This was a requirement since v2.2 days, but it
usually worked nevertheless.

[   17.504959] ------------[ cut here ]------------
[   17.505488] WARNING: CPU: 0 PID: 93 at drivers/usb/core/hcd.c:1587 usb_hcd_map_urb_for_dma+0x37c/0x570
[   17.506545] transfer buffer not dma capable
[   17.507022] Modules linked in:
[   17.507370] CPU: 0 PID: 93 Comm: i2cdetect Not tainted 4.11.0-rc8+ #10
[   17.508103] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[   17.509039] Call Trace:
[   17.509320]  ? dump_stack+0x5c/0x78
[   17.509714]  ? __warn+0xbe/0xe0
[   17.510073]  ? warn_slowpath_fmt+0x5a/0x80
[   17.510532]  ? nommu_map_sg+0xb0/0xb0
[   17.510949]  ? usb_hcd_map_urb_for_dma+0x37c/0x570
[   17.511482]  ? usb_hcd_submit_urb+0x336/0xab0
[   17.511976]  ? wait_for_completion_timeout+0x12f/0x1a0
[   17.512549]  ? wait_for_completion_timeout+0x65/0x1a0
[   17.513125]  ? usb_start_wait_urb+0x65/0x160
[   17.513604]  ? usb_control_msg+0xdc/0x130
[   17.514061]  ? usb_xfer+0xa4/0x2a0
[   17.514445]  ? __i2c_transfer+0x108/0x3c0
[   17.514899]  ? i2c_transfer+0x57/0xb0
[   17.515310]  ? i2c_smbus_xfer_emulated+0x12f/0x590
[   17.515851]  ? _raw_spin_unlock_irqrestore+0x11/0x20
[   17.516408]  ? i2c_smbus_xfer+0x125/0x330
[   17.516876]  ? i2c_smbus_xfer+0x125/0x330
[   17.517329]  ? i2cdev_ioctl_smbus+0x1c1/0x2b0
[   17.517824]  ? i2cdev_ioctl+0x75/0x1c0
[   17.518248]  ? do_vfs_ioctl+0x9f/0x600
[   17.518671]  ? vfs_write+0x144/0x190
[   17.519078]  ? SyS_ioctl+0x74/0x80
[   17.519463]  ? entry_SYSCALL_64_fastpath+0x1e/0xad
[   17.519959] ---[ end trace d047c04982f5ac50 ]---

Cc: <stable@vger.kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Till Harbaum <till@harbaum.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>