arm64/configs: support channel extension

Bug: 196889889
Test: 1. Phone sanity test
      2. Emergency call with multiple PDNs connected
Signed-off-by: Namkyu Kim <namkyu78.kim@samsung.com>
Change-Id: I84d6859327b8d61598acb8ecb554c604749e6d6e
Signed-off-by: Mars Lin <marslin@google.com>

arch/arm64/configs/slider_gki.fragment

@@ -81,6 +81,7 @@ CONFIG_CP_WRESET_WA=m
 CONFIG_CP_THERMAL=m
 CONFIG_SUSPEND_DURING_VOICE_CALL=m
 CONFIG_MODEM_IF_LEGACY_QOS=m
+CONFIG_CH_EXTENSION=m
 CONFIG_VIDEO_EXYNOS_MFC=m
 CONFIG_EXYNOS_BTS=m
 CONFIG_BIGOCEAN=m