mtd: spi-nor: spansion: Determine current address mode

Internal address mode (3- or 4-byte) affects to the address length in
Read Any Reg op. Read Any Reg op is used in SMPT parse and other setup
functions. Current driver assumes that address mode is factory default
but users can change it via volatile and non-volatile registers.

Current address mode can be checked by CFR2V[7] but Read Any Reg op is
needed to read CFR2V (chicken-and-egg).

Introduce a way to determine current address mode by comparing status
register 1 values read by different address length.

Suggested-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Signed-off-by: Takahiro Kuwano <Takahiro.Kuwano@infineon.com>
Link: https://lore.kernel.org/r/20230331074606.3559258-11-tudor.ambarus@linaro.org
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>