Currently the SRAM location is fixed for all the boards derived from
qemu_cortex_a53. While this is acceptable when the image is directly
loaded in SRAM by QEMU, in some cases Zephyr can be loaded in RAM by
another piece of software or by semihosting at a different address
before jumping into it.
When for example TF-A is used and Zephyr is run as BL33 payload using
QEMU, in this case the default location in RAM is at a different
address (when preloaded BL33 base address is not used).
To address these cases, move the SRAM location into the board-specific
DTS so that it can be adjusted on a board by board basis.
Signed-off-by: Carlo Caione <ccaione@baylibre.com>