riscv: Add kmemleak support

Tested using syzkaller in QEMU's riscv64 virt machine.
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/Kconfig

@@ -56,6 +56,7 @@ config RISCV
 	select HAVE_ASM_MODVERSIONS
 	select HAVE_CONTEXT_TRACKING
 	select HAVE_COPY_THREAD_TLS
+	select HAVE_DEBUG_KMEMLEAK
 	select HAVE_DMA_CONTIGUOUS if MMU
 	select HAVE_EBPF_JIT if MMU
 	select HAVE_FUTEX_CMPXCHG if FUTEX