configure: Use uniform description for devel packages

As all other devel packages are written in the form "name devel",
use this form for libcap devel and libattr devel, too.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

configure

@@ -4611,7 +4611,7 @@ if test "$softmmu" = yes ; then
       tools="$tools fsdev/virtfs-proxy-helper\$(EXESUF)"
     else
       if test "$virtfs" = yes; then
-        error_exit "VirtFS is supported only on Linux and requires libcap-devel and libattr-devel"
+        error_exit "VirtFS is supported only on Linux and requires libcap devel and libattr devel"
       fi
       virtfs=no
     fi