mfd: exynos-lpass: Drop unneeded syscon.h include

syscon regmap is not used since commit addebf15 ("mfd: exynos-lpass:
Remove pad retention control").

Fixes: addebf15 ("mfd: exynos-lpass: Remove pad retention control")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20220202151310.285561-3-krzysztof.kozlowski@canonical.com