arm64: dts: exynos: drop unneeded syscon phandle in Exynos5433 LPASS

Exynos5433 LPASS audio node does not use syscon phandle since commit
addebf15 ("mfd: exynos-lpass: Remove pad retention control").  It
was also dropped from bindings.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Link: https://lore.kernel.org/r/20220129175332.298666-2-krzysztof.kozlowski@canonical.com