Only show CONFIG_PS2_KEYBOARD_SPINUP when CONFIG_COREBOOT.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
diff --git a/src/Kconfig b/src/Kconfig
index 2195bad..15485ac 100644
--- a/src/Kconfig
+++ b/src/Kconfig
@@ -126,7 +126,7 @@
         help
             Support PS2 ports (keyboard and mouse).
     config PS2_KEYBOARD_SPINUP
-        depends on PS2PORT
+        depends on PS2PORT && COREBOOT
         int "Extra time (in ms) to allow a keyboard to initialize"
         default 0
         help