spi: spi_flash_probe_bus_cs() rely on DT for spi speed and mode

spi: spi_flash_probe_bus_cs() rely on DT for spi speed and mode

Now, spi_flash_probe_bus_cs() relies on DT for spi speed and mode
and logically calls spi_get_bus_and_cs(). In case spi mode and speed are
not read from DT, make usage of spi_flash_probe() instead.

To sum-up:
 - Previous call tree was:
    spi_flash_probe() -> spi_flash_probe_bus_cs() -> spi_get_bus_and_cs()

 - Current call tree is:
    spi_flash_probe() -> _spi_get_bus_and_cs()
    spi_flash_probe_bus_cs() -> spi_get_bus_and_cs()

This patch impacts the following :
  - cmd/sf.c: if spi mode and/or speed is passed in argument of
    do_spi_flash_probe(), call spi_flash_probe() otherwise call
    spi_flash_probe_bus_cs().

  - drivers/net/fm/fm.c: as by default spi speed and mode was set to
    0 and a comment indicates that speed and mode are read from DT,
    use spi_flash_probe_bus_cs().

  - drivers/net/pfe_eth/pfe_firmware.c: spi speed and mode are not read
    from DT by all platforms using this driver, so keep legacy and replace
    spi_flash_probe_bus_cs() by spi_flash_probe();

  - drivers/net/sni_netsec.c : spi speed and mode are not read from DT,
    so replace spi_flash_probe_bus_cs() by spi_flash_probe().

  - drivers/usb/gadget/max3420_udc.c: Can't find any platform which make
    usage of this driver, nevertheless, keep legacy and replace
    spi_get_bus_and_cs() by _spi_get_bus_and_cs().

  - env/sf.c: a comment indicates that speed and mode are read
    from DT. So use spi_flash_probe_bus_cs().

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Cc: Marek Behun <marek.behun@nic.cz>
Cc: Jagan Teki <jagan@amarulasolutions.com>
Cc: Vignesh R <vigneshr@ti.com>
Cc: Joe Hershberger <joe.hershberger@ni.com>
Cc: Ramon Fried <rfried.dev@gmail.com>
Cc: Lukasz Majewski <lukma@denx.de>
Cc: Marek Vasut <marex@denx.de>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Cc: Stefan Roese <sr@denx.de>
Cc: "Pali Rohár" <pali@kernel.org>
Cc: Konstantin Porotchkin <kostap@marvell.com>
Cc: Igal Liberman <igall@marvell.com>
Cc: Bin Meng <bmeng.cn@gmail.com>
Cc: Pratyush Yadav <p.yadav@ti.com>
Cc: Sean Anderson <seanga2@gmail.com>
Cc: Anji J <anji.jagarlmudi@nxp.com>
Cc: Biwen Li <biwen.li@nxp.com>
Cc: Priyanka Jain <priyanka.jain@nxp.com>
Cc: Chaitanya Sakinam <chaitanya.sakinam@nxp.com>