MAINTAINERS: add Konrad as the SWIOTLB maintainer

Now that I've an IA64 box on top of the other boxes (IBM with Calgary-X,
Intel VT-d, AMD Vi, and AMD GART - that can use SWIOTLB as fallback) I can
reliably do regression testing.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>