x86: Don't panic if can not alloc buffer for swiotlb

x86: Don't panic if can not alloc buffer for swiotlb

Normal boot path on system with iommu support:
swiotlb buffer will be allocated early at first and then try to initialize
iommu, if iommu for intel or AMD could setup properly, swiotlb buffer
will be freed.

The early allocating is with bootmem, and could panic when we try to use
kdump with buffer above 4G only, or with memmap to limit mem under 4G.
for example: memmap=4095M$1M to remove memory under 4G.

According to Eric, add _nopanic version and no_iotlb_memory to fail
map single later if swiotlb is still needed.

-v2: don't pass nopanic, and use -ENOMEM return value according to Eric.
     panic early instead of using swiotlb_full to panic...according to Eric/Konrad.
-v3: make swiotlb_init to be notpanic, but will affect:
     arm64, ia64, powerpc, tile, unicore32, x86.
-v4: cleanup swiotlb_init by removing swiotlb_init_with_default_size.

Suggested-by: Eric W. Biederman <[email protected]>
Signed-off-by: Yinghai Lu <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Reviewed-and-tested-by: Konrad Rzeszutek Wilk <[email protected]>
Cc: Joerg Roedel <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: Jeremy Fitzhardinge <[email protected]>
Cc: Kyungmin Park <[email protected]>
Cc: Marek Szyprowski <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Andrzej Pietrasiewicz <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: Shuah Khan <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>