arm64: versal-net: spi: Update boot sequence dynamically

arm64: versal-net: spi: Update boot sequence dynamically

Currently xspi0 is used for all spi boot modes, it means it will use "sf
probe 0 0 0" for all spi's irrespective of which node it is wired.

Get boot sequence from dev_seq() and update boot command for xspi
dynamically.

As a result bootcmd for spi is updated as below when two instances of spi
are present in DT node.
bootcmd_xspi0=devnum_xspi=0; run xspi_boot
bootcmd_xspi1=devnum_xspi=1; run xspi_boot

xspi_boot=sf probe $devnum_xspi:0 0 0 && sf read $scriptaddr
$script_offset_f $script_size_f && echo XSPI: Trying to boot script at
${scriptaddr} && source ${scriptaddr}; echo XSPI: SCRIPT FAILED:
continuing...;

Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@amd.com>
Link: https://lore.kernel.org/r/20230614093058.30438-1-ashok.reddy.soma@amd.com
Signed-off-by: Michal Simek <michal.simek@amd.com>