tests: mem_protect/mem_map: enable userspace on qemu_x86_tiny

Due to qemu_x86_tiny having very small defined SRAM area,
enabling userspace results in not having enough free physical
pages to run the tests. So make the memory a bit larger so
we can actually test memory mapping with userspace.

Fixes #46398

Signed-off-by: Daniel Leung <daniel.leung@intel.com>