tools/mkeficapsule.c: fix DEBUG build

Fix a missing comma sign (,) from a printf(), that is only
reachable if DEBUG is defined, in which case the build fails with:

    tools/mkeficapsule.c:266:36: error: expected ‘)’ before ‘bin’
      266 |  printf("\tbin: %s\n\ttype: %pUl\n" bin, guid);
          |                                    ^~~~
          |                                    )

Signed-off-by: Klaus Heinrich Kiwi <klaus@linux.vnet.ibm.com>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>