reset: rzv2h-usb2phy: Convert to regmap API

reset: rzv2h-usb2phy: Convert to regmap API

Replace raw MMIO accesses (readl/writel) with regmap_read() and
regmap_multi_reg_write() via devm_regmap_init_mmio().
Drop the manual spinlock as regmap provides internal locking.

Replace the custom rzv2h_usb2phy_regval struct with the standard
reg_sequence, and encode assert/deassert sequences as reg_sequence
arrays rather than individual scalar fields in the of_data
descriptor.

Use the reg_sequence .delay_us field to encode the 11 µs post-assert
delay, replacing the explicit usleep_range(11, 20) call in
rzv2h_usbphy_reset_assert().

Select REGMAP_MMIO in Kconfig.

Signed-off-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>