Fix a typo in xc_lib.c.

Signed-off-by: Wei Gang <gang.wei@intel.com>

diff -r 410ba927e6a6 tools/ocaml/libs/xc/xc_lib.c
--- a/tools/ocaml/libs/xc/xc_lib.c	Wed Dec 01 21:39:39 2010 +0800
+++ b/tools/ocaml/libs/xc/xc_lib.c	Wed Dec 01 21:58:07 2010 +0800
@@ -1522,7 +1522,7 @@ int xc_domain_set_hpet(int handle, unsig
 
 int xc_domain_set_vpt_align(int handle, unsigned int domid, int vpt_align)
 {
-	return xc_set_hvm_param(handle, domid, HVM_PARAM_HPET_ENABLED, (unsigned long) vpt_align);
+	return xc_set_hvm_param(handle, domid, HVM_PARAM_VPT_ALIGN, (unsigned long) vpt_align);
 }
 
 int xc_domain_get_acpi_s_state(int handle, unsigned int domid)