configs: j721e_evm_a72: Align OSPI partitions on erase block boundary

S28HS512T on TI SK has sector size of 256KB, so update OSPI partition
to align on 256KB sector size. Since the sector size for MT35XU512ABA
on EVM is 128KB, partitions will remain aligned for EVM.

Also, now since the sector size is 256KB ospi.env.backup will collide
with ospi.sysfw, so move ospi.env.backup to the padding space (0x7C0000)
before ospi.rootfs partition.

Signed-off-by: Sinthu Raja <sinthu.raja@ti.com>