Patch from Richard Purdie

Add functions to generate backtraces of both kernel and user processes
which allows oprofile's call graphing functionality to be used on arm.
This requires unstripped binaries/libs which use a frame pointer.

Signed-off-by: Richard Purdie
Signed-off-by: Zwane Mwaikambo <zwane@arm.linux.org.uk>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>