refactor(mm): use typedefs

* Add typedefs for memory modes and attrs
* Add typedef for page table levels
* Add typedef for the ptable ASID
* Rewrite `MM_MODE_` macros to use shifts instead of writing the
  value manually.

Change-Id: I783825777b4897692d48287fc689026a04ecba50
Signed-off-by: Karl Meakin <karl.meakin@arm.com>
diff --git a/src/vcpu.c b/src/vcpu.c
index 4fa3765..114048b 100644
--- a/src/vcpu.c
+++ b/src/vcpu.c
@@ -141,7 +141,7 @@
 			    struct vcpu_fault_info *f)
 {
 	struct vm *vm = current->vm;
-	uint32_t mode;
+	mm_mode_t mode;
 	uint32_t mask = f->mode | MM_MODE_INVALID;
 	bool resume;
 	struct vm_locked locked_vm;