Add p9_nv_ref_clk_enable to makefile
Add p9_nv_ref_clk_enable to makefile

Change-Id: I0b2d8c098f114dd64865a1f3131c54f6d91246fb
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/31784
Tested-by: Jenkins Server <8e3f934e4c44875bc48d33da3ea13d93ba9a233f@us.ibm.com>
Tested-by: FSP CI Jenkins <aa9e4d9ac7cd25905e9c0dd36d4150516e73dd86@us.ibm.com>
Reviewed-by: Daniel M. Crowell <912029ca9254ac7b5854e56910561d682e1fa2d0@us.ibm.com>

open-power/hostboot,open-power/hostboot,open-power/hostboot,open-power/hostboot,open-power/hostboot