mmu: first attempt to get it enabled

Signed-off-by: Sean Cross <sean@xobs.io>

asm.S

@@ -0,0 +1,26 @@
+#if __riscv_xlen == 64
+# define STORE    sd
+# define LOAD     ld
+# define LOG_REGBYTES 3
+#else
+# define STORE    sw
+# define LOAD     lw
+# define LOG_REGBYTES 2
+#endif
+#define REGBYTES (1 << LOG_REGBYTES)
+
+.global start_kmain
+.text
+start_kmain:
+    li		t0, (1 << 11) | (1 << 5)
+	csrw	mstatus, t0
+	csrw	mepc, a0
+    add     a0, a1, zero
+    add     a1, a2, zero
+    add     a2, a3, zero
+    add     a3, a4, zero
+    add     a4, a5, zero
+    add     a5, a6, zero
+    add     a6, a7, zero
+    add     a7, zero, zero
+	mret    // Return to kmain