devtools: fix result of svg include check

devtools: fix result of svg include check

Fix trivial bug. In sh shell, 'foo = 1' is not the same as
'foo=1'. Using 'foo = 1' makes the shell attempt to interpret foo
as a command, rather than a simple variable assignment.

Fixes: dafc04c15174 ("devtools: fix return of forbidden addition checks")
Cc: stable@dpdk.org
Signed-off-by: Michael Santana <msantana@redhat.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>