libcacard: pkgconfig: tidy dependent libs

libcacard.pc file lists only one package in Requires
field, which is nss, while glib-2.0 is also a requiriment.
Furthermore, for libraries used internally by the library
(this is the way nss and glib are used by libcacard),
Requires.private shold be used instead of Requires.

Fix both issues.

This does not affect linking of qemu because it links
with objects from libcacard directly.
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

libcacard/libcacard.pc.in

@@ -7,7 +7,7 @@ Name: cacard
 Description: CA Card library
 Version: @VERSION@
 
-Requires:  nss
+Requires.private: nss glib-2.0
 Libs: -L${libdir} -lcacard
 Libs.private:
 Cflags: -I${includedir}