Impact: Section fix

WARNING: vmlinux.o(.text+0x596d2): Section mismatch in
reference from the function swiotlb_dma_init() to the function
.init.text:swiotlb_init()
The function swiotlb_dma_init() references
the function __init swiotlb_init().
This is often because swiotlb_dma_init lacks a __init
annotation or the annotation of swiotlb_init is wrong.
Signed-off-by: NTony Luck <tony.luck@intel.com>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>