Fix generic __memcpy_chk implementation.

- Clean up the labels (add .L to make them local).
- Change to using cfi directives.
- Fix unwinding of the __memcpy_chk fail path.

Bug: 18033671

(cherry pick from commit 7123d4371a5e04337b1de5f8cdf6cdc1e08e9cad)

Change-Id: Ife93bcbfc1949ef29fc8e2dc515b7120632b82b1
1 file changed