exynos5: pinmux: check flag for i2c config

Some versions of Exynos5 supports High-Speed I2C,
on few interfaces, this change allows support this.
The new flag is: PINMUX_FLAG_HS_MODE

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Akshay Saraswat <akshay.s@samsung.com>
Cc: Minkyu Kang <mk7.kang@samsung.com>
Acked-by: Simon Glass <sjg@chromium.org>