scons: Don't list cell as a driver.
Cell driver's SConscript never got written, and it is not trivial one to
write, so don't accept cell in the driver option to avoid confusion.
diff --git a/SConstruct b/SConstruct
index ed92518..787ff6e 100644
--- a/SConstruct
+++ b/SConstruct
@@ -46,7 +46,7 @@
opts.Add(ListVariable('statetrackers', 'state trackers to build', default_statetrackers,
['mesa', 'python', 'xorg']))
opts.Add(ListVariable('drivers', 'pipe drivers to build', default_drivers,
- ['softpipe', 'failover', 'svga', 'i915', 'i965', 'cell', 'trace', 'r300', 'identity', 'llvmpipe']))
+ ['softpipe', 'failover', 'svga', 'i915', 'i965', 'trace', 'r300', 'identity', 'llvmpipe']))
opts.Add(ListVariable('winsys', 'winsys drivers to build', default_winsys,
['xlib', 'vmware', 'intel', 'i965', 'gdi', 'radeon']))