configs: k2x_evm: Reorder default boot command

We first split the CONFIG_BOOTCOMMAND into its components to improve
readability. We then make the following order changes:

 - Run findfdt first so the fdt name can be used in envboot like OMAP
 - Install the boot monitor before running the PMMC so we can make any
     needed secure changes before PMMC, do this on both HS and non-HS
 - Move set_name_pmmc to just before get_pmmc_${boot}

Signed-off-by: Andrew F. Davis <afd@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>