av1.cmake: exclude highbd_pickrst_sve.c w/realtime-only

Fixes warning with `-DCONFIG_REALTIME_ONLY=1`:
av1/encoder/arm/highbd_pickrst_sve.c|85 col 6| warning: no previous
  prototype for function 'av1_compute_stats_highbd_sve'
  [-Wmissing-prototypes]

Change-Id: Ica25f86787c2de101760102cc6298dd182e2e724
diff --git a/av1/av1.cmake b/av1/av1.cmake
index f5d7057..d702e25 100644
--- a/av1/av1.cmake
+++ b/av1/av1.cmake
@@ -670,6 +670,7 @@
                    "${AOM_ROOT}/av1/encoder/arm/temporal_filter_neon_dotprod.c")
 
   list(REMOVE_ITEM AOM_AV1_ENCODER_INTRIN_SVE
+                   "${AOM_ROOT}/av1/encoder/arm/highbd_pickrst_sve.c"
                    "${AOM_ROOT}/av1/encoder/arm/pickrst_sve.c")
 
   list(REMOVE_ITEM AOM_AV1_ENCODER_SOURCES