USB: ehci-s5p: add DMA burst support

DMA burst support is added to improve performance in EHCI data
transfer. The USB EHCI controller on Exynos SoCs can use INCR16,
INCR8, and INCR4 mode. These modes of INSNREG00 register should
be set in order to enable DMA burst transfer. This feature is
also related to AHB spec.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Sangwook Lee <sangwook.lee@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>