[mlir][tosa] Move cond_if and while_loop operations to controlflow extension (#128216)
This commit adds the concept of a controlflow extension to the dialect
and updates the validation pass to check conf_if and while_loop are
supported only in the presence of the controlflow extension.
Signed-off-by: Luke Hutton <luke.hutton@arm.com>
Co-authored-by: Luke Hutton <luke.hutton@arm.com>