qrtr: Convert qrtr_ports from IDR to XArray

The XArray interface is easier for this driver to use.  Also fixes a
bug reported by the improper use of GFP_ATOMIC.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>