mtd: spi-nor: sfdp: introduce smpt_read_dummy fixup hook

mtd: spi-nor: sfdp: introduce smpt_read_dummy fixup hook

SMPT contains config detection info that describes opcode, address, and
dummy cycles to read sector map config. The dummy cycles parameter can
be SMPT_CMD_READ_DUMMY_IS_VARIABLE and in that case nor->read_dummy
(initialized as 0) is used. In Infineon flash chips, Read Any Register
command with variable dummy cycle is defined in SMPT. S25Hx/S28Hx flash
has 0 dummy cycle by default to read volatile regiters and
nor->read_dummy can work. S25FS-S flash has 8 dummy cycles so we need a
hook that can fix dummy cycles with actually used value.

Inroduce smpt_read_dummy() in struct spi_nor_fixups. It is called when
the dummy cycle field in SMPT config detection is 'varialble'.

Reviewed-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Tested-by: Marek Vasut <marek.vasut+renesas@mailbox.org> # S25FS512S
Signed-off-by: Takahiro Kuwano <Takahiro.Kuwano@infineon.com>
Signed-off-by: Pratyush Yadav <pratyush@kernel.org>