examples: eliminate CONFIG_STANDALONE_LOAD_ADDR

examples: eliminate CONFIG_STANDALONE_LOAD_ADDR

CONFIG_STANDALONE_LOAD_ADDR has been used for examples/standalone
but not for examples/api.

The suitability of an address to load an ELF binary and run it does
not only depend on the architecture but also on the memory layout of
the board which is not reflected in the default value of
CONFIG_STANDALONE_LOAD_ADDR.

Commit 32b7e39db4d3 ("Convert CONFIG_STANDALONE_LOAD_ADDR to Kconfig")
set the default on RISC-V to 0x0 though most boards used 0x80200000
before the patch.

On most boards we can assume 8 MiB of memory available above $loadaddr.
So we can safely use $loadaddr + 4 MiB as load address for the standalone
example and eliminate CONFIG_STANDALONE_LOAD_ADDR altogether.

Fixes: 32b7e39db4d3 ("Convert CONFIG_STANDALONE_LOAD_ADDR to Kconfig")
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>