Only compile recovery_code for riscv64

Recovery code depends on the internals of guest_state, which can only
support riscv64 for now. Ensure it only builds there and not for 32-bit.

Test: mm && tree-hugger
Bug: 278926583
Change-Id: I6a328ca8155e3d6ae88c7fd2fef0548dd1376090
1 file changed