spec: Require libiscsi-devel instead of libiscsi

Commit 34a6962c added a BuildRequires for the
iscsi-direct backend, but we need the headers rather
than the runtime package to be available in order to
link against the library.
Signed-off-by: NAndrea Bolognani <abologna@redhat.com>
Reviewed-by: NErik Skultety <eskultet@redhat.com>

libvirt.spec.in

@@ -320,7 +320,7 @@ BuildRequires: lvm2
 # For pool type=iscsi
 BuildRequires: iscsi-initiator-utils
 # For pool type=iscsi-direct
-BuildRequires: libiscsi
+BuildRequires: libiscsi-devel
 # For disk driver
 BuildRequires: parted-devel
 # For Multipath support