Fix makefile variables (#394)

Makefile

@@ -8,12 +8,12 @@ setup:
 	cargo install bootimage
 
 # Compilation options
-output = video, # video, serial
-keyboard = qwerty # qwerty, azerty, dvorak
+output = video# video, serial
+keyboard = qwerty# qwerty, azerty, dvorak
 
 # Emulation options
-nic = rtl8139 # rtl8139, pcnet
-audio = sdl # sdl, coreaudio
+nic = rtl8139# rtl8139, pcnet
+audio = sdl# sdl, coreaudio
 kvm = false
 
 export MOROS_KEYBOARD = $(keyboard)
@@ -49,7 +49,7 @@ image: $(img)
 	dd conv=notrunc if=$(bin) of=$(img)
 
 opts = -m 32 -drive file=$(img),format=raw \
-			 -audiodev driver=$(audio),id=a0 -machine pcspk-audiodev=a0 \
+			 -audiodev $(audio),id=a0 -machine pcspk-audiodev=a0 \
 			 -netdev user,id=e0,hostfwd=tcp::8080-:80 -device $(nic),netdev=e0
 ifeq ($(kvm),true)
 	opts += -cpu host -accel kvm