ACPI / PMIC: Add generic intel_soc_pmic_exec_mipi_pmic_seq_element handling

Most PMIC-s use only a single i2c-address, so after verifying the
i2c-address matches, we can simply pass the call to regmap_update_bits.

This commit adds support for this and hooks this up for the xpower AXP288
PMIC by setting the new pmic_i2c_address field.

This fixes the following errors on display on / off on a Jumper Ezpad
mini 3 and an Onda V80 plus tablet, both of which use the AXP288:

intel_soc_pmic_exec_mipi_pmic_seq_element: Not implemented
intel_soc_pmic_exec_mipi_pmic_seq_element: i2c-addr: 0x34 reg-addr ...
[drm:mipi_exec_pmic [i915]] *ERROR* mipi_exec_pmic failed, error: -95

Instead of these errors on both devices we now correctly turn on / off
DLDO3 (through direct register manipulation). On the Onda V80 plus this
fixes an issue with the backlight being brighter around the borders after
an off / on cycle. This should also help to save some power when the
display is off.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190107111556.4510-4-hdegoede@redhat.com