arm64: dts: uDPU: update partition table

Partition currently called "uboot" does not only contain U-boot, but
rather it contains TF-A, U-boot and U-boot environment.

So, to avoid accidentally deleting the U-boot environment which is
located at 0x180000 split the partition.

"uboot" is not the correct name as you can't boot these boards with U-boot
only, TF-A must be present as well, so rename the "uboot" partition to
"firmware".

While we are here, describe the NOR node as "spi-flash@0" instead of
"m25p80@0" which is the old SPI-NOR driver name.

This won't break booting for existing devices as the SoC-s BootROM is not
partition aware at all, it will simply try booting from 0x0 of the
boot device that is set by bootstrap pins.

This will however prevent accidental or automated flashing of just U-boot
to the partition.

Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Reviewed-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>