libs/hypfs: use correct zlib name in pc file

Its name is "zlib" not "z".

Reported-by: Olaf Hering <olaf@aepfle.de>
Fixes: 86234eafb9 ("libs: add libxenhypfs")
Signed-off-by: Wei Liu <wl@xen.org>
Reviewed-by: Juergen Gross <jgross@suse.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Release-acked-by: Paul Durrant <paul@xen.org>

tools/libs/hypfs/xenhypfs.pc.in

@@ -7,4 +7,4 @@ Description: The Xenhypfs library for Xen hypervisor
 Version: @@version@@
 Cflags: -I${includedir} @@cflagslocal@@
 Libs: @@libsflag@@${libdir} -lxenhypfs
-Requires.private: xentoolcore,xentoollog,xencall,z
+Requires.private: xentoolcore,xentoollog,xencall,zlib