ci/b2c: fix the `cmdline_extra` variable name
The variable name should have been named kernel_cmdline_extra
, so
let's rename it to match the expectations of the rest of Mesa.
Fixes: 4362d591 ("ci/b2c: import all variables starting with B2C_
")
Signed-off-by: Martin Roukala (né Peres) martin.roukala@mupuf.org