mfd/syscon.h header is no longer required since the update to
exynos_get_pmu_regmap_by_phandle() api.

Fixes: f2c6d0fa ("phy: samsung-ufs: use exynos_get_pmu_regmap_by_phandle() to obtain PMU regmap")
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Link: https://lore.kernel.org/r/20240426104129.2211949-2-peter.griffin@linaro.orgSigned-off-by: Vinod Koul <vkoul@kernel.org>