The driver was using CONFIG_SRAM_BASE_ADDRESS as the value used to
recognize whether source buffer is in RAM. This label provide the
base address of the image SRAM, and not the base of actual HW SRAM.
This patch uses nrfx_is_in_ram() instead.
fixes#29467
Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>