phy: miphy365x: Select GENERIC_PHY instead of depending on it

Enabling GENERIC_PHY in the shared (by most ARM sub-architectures)
defconfig multi_v7_defconfig is prohibited.  Instead, we'll enable
it from the Kconfig whenever PHY_MIPHY365X is enabled.

Cc: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>