src/lib: Fix typos

Change-Id: Ia1da6637cfca5ddbd0879ea271bc68bb881b92e3
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37563
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/lib/bootmem.c

@@ -274,7 +274,7 @@ void *bootmem_allocate_buffer(size_t size)
 		end = max_addr;
 	begin = end - size;
 
-	/* Mark buffer as unusuable for future buffer use. */
+	/* Mark buffer as unusable for future buffer use. */
 	bootmem_add_range(begin, size, BM_MEM_PAYLOAD);
 
 	return (void *)(uintptr_t)begin;