Move documentation file list to relevant make file

Change-Id: I2fe3095c4eb60233f00830d4124583ce7a64caa4

libs.mk

diff --git a/libs.mk b/libs.mk
index ef49828..4115dd8 100644
--- a/libs.mk
+++ b/libs.mk
@@ -29,6 +29,7 @@
 
 include $(SRC_PATH_BARE)/vpx/vpx_codec.mk
 CODEC_SRCS-yes += $(addprefix vpx/,$(call enabled,API_SRCS))
+CODEC_DOC_SRCS += $(addprefix vpx/,$(call enabled,API_DOC_SRCS))
 
 include $(SRC_PATH_BARE)/vpx_mem/vpx_mem.mk
 CODEC_SRCS-yes += $(addprefix vpx_mem/,$(call enabled,MEM_SRCS))
@@ -47,7 +48,6 @@
   CODEC_EXPORTS-yes += $(addprefix $(VP8_PREFIX),$(VP8_CX_EXPORTS))
   INSTALL-LIBS-yes += include/vpx/vp8.h include/vpx/vp8cx.h
   INSTALL_MAPS += include/vpx/% $(SRC_PATH_BARE)/$(VP8_PREFIX)/%
-  CODEC_DOC_SRCS += vpx/vp8.h vpx/vp8cx.h
   CODEC_DOC_SECTIONS += vp8 vp8_encoder
 endif
 
@@ -58,7 +58,6 @@
   CODEC_EXPORTS-yes += $(addprefix $(VP8_PREFIX),$(VP8_DX_EXPORTS))
   INSTALL-LIBS-yes += include/vpx/vp8.h include/vpx/vp8dx.h
   INSTALL_MAPS += include/vpx/% $(SRC_PATH_BARE)/$(VP8_PREFIX)/%
-  CODEC_DOC_SRCS += vpx/vp8.h vpx/vp8dx.h
   CODEC_DOC_SECTIONS += vp8 vp8_decoder
 endif
 
@@ -332,11 +331,6 @@
           $(RTCD_OPTIONS) $^ > $@
 CLEAN-OBJS += $(BUILD_PFX)vpx_rtcd.h
 
-CODEC_DOC_SRCS += vpx/vpx_codec.h \
-                  vpx/vpx_decoder.h \
-                  vpx/vpx_encoder.h \
-                  vpx/vpx_image.h
-
 ##
 ## libvpx test directives
 ##