npcx: adc: Add support for npcx7 series ec

This CL added the support for additional 5 adc channels on npcx7 series
ec. The pin-mux functionality of adc channels was already introduced in
CL 481561.

BRANCH=none
BUG=none
TEST=No build errors for all boards using npcx5 series.
     Build poppy board and upload FW to platform. No issues found.
     All 10 adc channels passed the test on npcx796f evb.

Change-Id: I2c7458958ff659fce78f265eefa160050dee7daf
Signed-off-by: Mulin Chao <mlchao@nuvoton.com>
Reviewed-on: https://chromium-review.googlesource.com/497526
Reviewed-by: Randall Spangler <rspangler@chromium.org>

chip/npcx/adc_chip.h

@@ -20,6 +20,13 @@ enum npcx_adc_input_channel {
 	NPCX_ADC_CH2,
 	NPCX_ADC_CH3,
 	NPCX_ADC_CH4,
+#if defined(CHIP_FAMILY_NPCX7)
+	NPCX_ADC_CH5,
+	NPCX_ADC_CH6,
+	NPCX_ADC_CH7,
+	NPCX_ADC_CH8,
+	NPCX_ADC_CH9,
+#endif
 	NPCX_ADC_CH_COUNT
 };