memory: samsung: exynos5422-dmc: remove unused exynos5_dmc members

The struct exynos5_dmc members bypass_rate, mx_mspll_ccore_phy,
mout_mx_mspll_ccore_phy and opp_bypass are not actually used.

Apparently there was a plan to store the OPP for the bypass mode in
opp_bypass member, but driver fails to do it and instead always sets
target voltage during bypass mode.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200822163218.21857-2-krzk@kernel.org