dpll: zl3073x: Add functions to access hardware registers

dpll: zl3073x: Add functions to access hardware registers

Besides the device host registers that are directly accessible, there
are also hardware registers that can be accessed indirectly via specific
host registers.

Add register definitions for accessing hardware registers and provide
helper functions for working with them. Additionally, extend the number
of pages in the regmap configuration to 256, as the host registers used
for accessing hardware registers are located on page 255.

Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Link: https://patch.msgid.link/20250909091532.11790-2-ivecera@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>