device/device.h: Fix spelling mistake

Fix spelling mistake added in 3e99ba0 "device: Add a helper function to
add a downstream bus".

Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Change-Id: I66ae5000f6f5c0e5bfe42bdfbbbcedec6df0c520
Reviewed-on: https://review.coreboot.org/c/coreboot/+/80234
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/device/device.c b/src/device/device.c
index 72a408e..88085f7 100644
--- a/src/device/device.c
+++ b/src/device/device.c
@@ -133,7 +133,7 @@
  * Allocate a new downstream bus structure below a device and attach it
  * to the device tree if the device doesn't already have a downstream bus.
  *
- * @param parent Parent device the to be created bus should be attached to.
+ * @param parent Parent device the to-be-created bus should be attached to.
  * @return Pointer to the newly created bus structure or the existing bus.
  *
  */