tools/libxl: cleanup the do_pci_add() function

tools/libxl: cleanup the do_pci_add() function

This function modifies the do_pci_add() function in libxl_pci.c
by unindenting a code block whose condition was removed in the
previous commit. The block was left as is to facilitate functional
review of the previous commit; this commit cleans it up.
This commit introduces no functional change.

Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>
Acked-by: Ian Campbell <Ian.Campbell@eu.citrix.com>
Cc: Dario Faggioli <dario.faggioli@citrix.com>
Cc: Paolo Valente <paolo.valente@unimore.it>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Julien Grall <julien.grall@citrix.com>
Cc: Jan Beulich <JBeulich@suse.com>
Cc: Ian Jackson <Ian.Jackson@eu.citrix.com>
Cc: Eric Trudeau <etrudeau@broadcom.com>
Cc: Viktor Kleinik <viktor.kleinik@globallogic.com>
Cc: Andrii Tseglytskyi <andrii.tseglytskyi@globallogic.com>