v7: Update DWARF2

H.J. Lu wrote:
Joey, Xuepeng, please correct me if I am wrong. In case of DRAP,
FP has aligned SP and CFA is defined with an expression.

0: 8d 4c 24 04 lea 0x4(%esp),%ecx
4: 83 e4 f0 and $0xfffffff0,%esp
7: ff 71 fc pushl -0x4(%ecx)
a: 55 push %ebp
b: 89 e5 mov %esp,%ebp
d: 83 ec 28 sub $0x28,%esp
10: 89 4c 24 1c mov %ecx,0x1c(%esp)

we still need to restore SP. exceptions won't work.

The CFA value is the old SP, so we can (and typically do) use that to
find it.

Jason