arm64: dts: ti: k3-am64-main: Update TF-A load address to workaround USB DFU limitation

Due to a limitation for USB DFU boot mode, SPL load address has to be less
than  or equal to 0x70001000. So, load address of SPL and TF-A have been
moved to 0x70000000 and 0x701c0000 respectively, in U-Boot version 2021.10.

Therefore, update TF-A's location in the device tree node.

Signed-off-by: Aswath Govindraju <a-govindraju@ti.com>
Reviewed-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Link: https://lore.kernel.org/r/20210616171224.24635-4-a-govindraju@ti.com