swiotlb: Don't include linux/swiotlb.h twice in lib/swiotlb.c

There's no point in including the linux/swiotlb.h header twice in
lib/swiotlb.c - this patch gets rid of the unneeded include.

Signed-off-by: Jesper Juhl <[e-mail]>
Signed-off-by: Ingo Molnar <[e-mail]>

lib/swiotlb.c

···
 #include <linux/spinlock.h>
 #include <linux/swiotlb.h>
 #include <linux/string.h>
-#include <linux/swiotlb.h>
 #include <linux/types.h>
 #include <linux/ctype.h>
 #include <linux/highmem.h>