Do not try to read/write device memory.

Device memory might have certain alignment constraints that the unwind
code violates. Since we shouldn't be reading this memory, treat this
type of memory as not readable and not writable.

Bug: 17037053

(cherry picked from commit f360ccc06f3f086f41cf6ba4036b52571ed2a54f)

Change-Id: I912e8645fe1f9223100d00559f9cea1f87931e45