Change test-emulate heap size and stack top
Change test-emulate heap size and stack top

The executables are linked at 0x7800_0000 (1920 MiB) which is
the top of the emulator RAM space, so the stack has been changed
to grow down from 0x7800_0000 (1920 MiB) and the size has been
changed to 0x0100_0000 (16 MiB).

rv8-io/rv8,rv8-io/rv8,rv8-io/rv8