drivers/iommu: Export core IOMMU API symbols to permit modular drivers

mainline inclusion
from mainline-v5.6-rc1
commit a7ba5c3d
category: bugfix
bugzilla: 30237, https://gitee.com/openeuler/kernel/issues/I6H9U5
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a7ba5c3d008dd78d881a1658eae5a2275ebd5087



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Building IOMMU drivers as modules requires that the core IOMMU API
symbols are exported as GPL symbols.

Signed-off-by: Will Deacon <will@kernel.org>
Tested-by: John Garry <john.garry@huawei.com> # smmu v3
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Guo Mengqi <guomengqi3@huawei.com>
Reviewed-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>