USB: isp1760: Fix endianness-sensitivity in of_isp1760_probe()

Data read direct from device tree properties will be in the device
tree's native endianness (i.e., big-endian).

This patch uses of_property_read_u32() to read the bus-width
property in host byte order instead.

Signed-off-by: Dave Martin <dave.martin@linaro.org>
Acked-by: Pawel Moll <pawel.moll@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>