usb: gadget: udc: renesas_usb3: Fix sysfs interface of "role"

usb: gadget: udc: renesas_usb3: Fix sysfs interface of "role"

BugLink: https://bugs.launchpad.net/bugs/1841652
commit 5dac665cf403967bb79a7aeb8c182a621fe617ff upstream.

Since the role_store() uses strncmp(), it's possible to refer
out-of-memory if the sysfs data size is smaller than strlen("host").
This patch fixes it by using sysfs_streq() instead of strncmp().

Fixes: cc995c9ec118 ("usb: gadget: udc: renesas_usb3: add support for usb role swap")
Cc: <stable@vger.kernel.org> # v4.12+
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>