You almost surely want to say N here.
+config MACH_MP1000
+ bool "MACH_MP1000"
+ help
+ Say Y if you intend to run the kernel on the Comdial MP1000 platform.
+
+config MP1000_90MHZ
+ bool "MP1000_90MHZ"
+ depends on MACH_MP1000
+ help
+ Say Y if you have the MP1000 configured to be set at 90MHZ rather than 74MHZ
+
endmenu
endif