payloads: change coreboot to lowercase

The word 'coreboot' should always be written in lowercase, even at the
start of a sentence.

Change-Id: I2ec18ca55e0ea672343a951ab81a24a5630f45fd
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/20028
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Philippe Mathieu-Daudé <philippe.mathieu.daude@gmail.com>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>

payloads/libpayload/libc/malloc.c

@@ -94,7 +94,7 @@ void init_dma_memory(void *start, u32 size)
 	}
 
 	/*
-	 * DMA memory might not be zeroed by Coreboot on stage loading, so make
+	 * DMA memory might not be zeroed by coreboot on stage loading, so make
 	 * sure we clear the magic cookie from last boot.
 	 */
 	*(hdrtype_t *)start = 0;