arm: Change text base address for 32 bit tests when running under kvmtool

The 32 bit tests do not have relocation support and rely on the build
system to set the text base address to 0x4001_0000, which is the memory
location where the test is placed by qemu. However, kvmtool loads a payload
at a different address, 0x8000_8000, when loading a test with --kernel.
When using --firmware, the default is 0x8000_0000, but that can be changed
with the --firmware-address comand line option.

When 32 bit tests are configured to run under kvmtool, set the text base
address to 0x8000_8000.

Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Andrew Jones <drjones@redhat.com>