arm: a37xx: espressobin: Fix non-working SPI

arm: a37xx: espressobin: Fix non-working SPI

Commit 0934dddc6436 ("arm: a37xx: Update DTS files to version from
upstream Linux kernel") ported Linux's device-tree files for Armada 3720
SOCs. This broke SPI support on some Espressobin boards and results in
following U-Boot error:

  Loading Environment from SPIFlash... jedec_spi_nor flash@0: unrecognized JEDEC id bytes: f7, 30, 0b
  *** Warning - spi_flash_probe_bus_cs() failed, using default environment

Before that commit DT node for SPI was called 'spi-flash@0' and after
that commit it is called 'flash@0'. Before that commit 'spi-max-frequency'
was set to 50000000 and after it is 104000000.

Rename DT node 'spi-flash@0 in armada-3720-espressobin-u-boot.dtsi to
'flash@0' and set custom U-Boot 'spi-max-frequency' back to 50000000.

With this change SPI is working on Espressobin again and it is detected
with JEDEC ids ef, 60, 16 on our tested unit.

  Loading Environment from SPIFlash... SF: Detected w25q32dw with page size 256 Bytes, erase size 4 KiB, total 4 MiB
  OK

Note that it is unknown why spi-max-frequency with value 104000000 does not
work in U-Boot as it works fine with Linux kernel. Also note that in
defconfig file configs/mvebu_espressobin-88f3720_defconfig is set option
CONFIG_SF_DEFAULT_SPEED=40000000 which is different value than in DT.

Fixes: 0934dddc6436 ("arm: a37xx: Update DTS files to version from upstream Linux kernel")
Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>