winsys/radeon: add command stream replay dump for faulty lockup v3

winsys/radeon: add command stream replay dump for faulty lockup v3

Build time option, set RADEON_CS_DUMP_ON_LOCKUP to 1 in radeon_drm_cs.h to
enable it.

When enabled after each cs submission the code will try to detect lockup by
waiting on one of the buffer of the cs to become idle, after a timeout it
will consider that the cs triggered a lockup and will write a radeon_lockup.c
file in current directory that have all information for replaying the cs.

To build this file :
gcc -O0 -g radeon_lockup.c -ldrm -o radeon_lockup -I/usr/include/libdrm

v2: Add radeon_ctx.h file to mesa git tree
v3: Slightly improve dumped file for easier editing, only dump first faulty cs

Signed-off-by: Jerome Glisse <jglisse@redhat.com>