[Keyboard] Reduce compile size for melgeek mach80 (#15034)

keyboards/melgeek/mach80/keymaps/via/rules.mk

@@ -1,2 +1 @@
 VIA_ENABLE = yes
-LTO_ENABLE = yes

keyboards/melgeek/mach80/rev1/rules.mk

@@ -21,4 +21,6 @@ RGBLIGHT_ENABLE = no           # Enable keyboard RGB underglow
 RGB_MATRIX_ENABLE = yes        # Use RGB matrix
 RGB_MATRIX_DRIVER = IS31FL3741
 
+LTO_ENABLE = yes
+
 LAYOUTS = tkl_ansi