iommu/amd: Fix backport of 140456f994195b568ecd7fc2287a34eadffef3ca

Clang warns:

drivers/iommu/amd_iommu.c:1335:6: warning: variable 'flags' is used
uninitialized whenever 'if' condition is true
[-Wsometimes-uninitialized]
        if (!pte)
            ^~~~
drivers/iommu/amd_iommu.c:1352:40: note: uninitialized use occurs here
        spin_unlock_irqrestore(&domain->lock, flags);
                                              ^~~~~
drivers/iommu/amd_iommu.c:1335:2: note: remove the 'if' if its condition
is always false
        if (!pte)
        ^~~~~~~~~
drivers/iommu/amd_iommu.c:1331:21: note: initialize the variable 'flags'
to silence this warning
        unsigned long flags;
                           ^
                            = 0
1 warning generated.

The backport of commit 140456f99419 ("iommu/amd: Fix sleeping in atomic
in increase_address_space()") to 4.9 as commit 1d648460 ("iommu/amd:
Fix sleeping in atomic in increase_address_space()") failed to keep the
"return false", which in 4.9 needs to be a regular "return" due to a
lack of commit f15d9a992f90 ("iommu/amd: Remove domain->updated").

This resolves the warning and matches the 4.14-4.19 backport.

Cc: Andrey Ryabinin <arbn@yandex-team.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Will Deacon <will@kernel.org>
Fixes: 1d648460 ("iommu/amd: Fix sleeping in atomic in increase_address_space()")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>