anv/cmd_buffer: Pull the undefined layout condition into the if

anv/cmd_buffer: Pull the undefined layout condition into the if

Now that this isn't a multi-case if and it's just the one case, it's a
bit clearer if the condition is just part of the if instead of being
pulled out into a boolean variable.

Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Reviewed-by: Nanley Chery <nanley.g.chery@intel.com>