mtd: rawnand: sunxi: rework pattern found registers

mtd: rawnand: sunxi: rework pattern found registers

On H6/H616, the register ECC_PAT_FOUND is at its own address, and not
part of ECC status register.
So, introduce the pattern found register offset in sunxi_nfc_caps, along
with its mask.

Also, introduce a non compile-time field_get() because FIELD_GET() and
u32_get_bits() don't work with non compile-time constant.

No functional change.

Link: https://lore.kernel.org/all/cover.1761588465.git.geert+renesas@glider.be
Signed-off-by: Richard Genoud <richard.genoud@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>