dpll: Make ZL3073X invisible

Currently, the user is always asked about the Microchip Azurite
DPLL/PTP/SyncE core driver, even when I2C and SPI are disabled, and thus
the driver cannot be used at all.

Fix this by making the Kconfig symbol for the core driver invisible
(unless compile-testing), and selecting it by the bus glue sub-drivers.
Drop the modular defaults, as drivers should not default to enabled.

Fixes: 2df8e64e ("dpll: Add basic Microchip ZL3073x support")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/97804163aeb262f0e0706d00c29d9bb751844454.1753874405.git.geert+renesas@glider.be


Signed-off-by: Jakub Kicinski <kuba@kernel.org>