adc: some symbols didn't have depends on ADC and should

I noticed that even though I was building w/o ADC, that some
ADC config symbols were still defined. Adding some "depends on"
to clean that up.

Change-Id: Ie73d131ba1ad63b5f3d920e17b4c7b5a0d785609
Signed-off-by: Chuck Jordan <cjordan@synopsys.com>

drivers/adc/Kconfig

@@ -35,6 +35,7 @@ config  ADC_DEBUG
 
 config ADC_INIT_PRIORITY
 	int
+	depends on ADC
 	default 80
 	prompt "Init priority"
 	help
@@ -42,10 +43,12 @@ config ADC_INIT_PRIORITY
 
 config  ADC_0_NAME
 	string "ADC Driver's name"
+	depends on ADC
 	default "ADC_0"
 
 config ADC_0_IRQ_PRI
         int
+	depends on ADC
         prompt "ADC interrupt priority"
         default 2