crash_dump/dm-crypt: don't print in arch-specific code

Patch series "kdump: Enable LUKS-encrypted dump target support in ARM64
and PowerPC", v5.

CONFIG_CRASH_DM_CRYPT has been introduced to support LUKS-encrypted device
dump target by addressing two challenges [1],

- Kdump kernel may not be able to decrypt the LUKS partition. For some
machines, a system administrator may not have a chance to enter the
password to decrypt the device in kdump initramfs after the 1st kernel
crashes

- LUKS2 by default use the memory-hard Argon2 key derivation function
which is quite memory-consuming compared to the limited memory reserved
for kdump.

To also enable this feature for ARM64 and PowerPC, we need to add a device
tree property dmcryptkeys [2] as similar to elfcorehdr to pass the memory
address of the stored info of dm-crypt keys to the kdump kernel.


This patch (of 3):

When the vmcore dumping target is not a LUKS-encrypted target, it's
expected that there is no dm-crypt key thus no need to return -ENOENT.
Also print more logs in crash_load_dm_crypt_keys. The benefit is
arch-specific code can be more succinct.

Link: https://lkml.kernel.org/r/20260225060347.718905-1-coxu@redhat.com
Link: https://lkml.kernel.org/r/20260225060347.718905-2-coxu@redhat.com
Link: https://lore.kernel.org/all/20250502011246.99238-1-coxu@redhat.com/ [1]
Link: https://github.com/devicetree-org/dt-schema/pull/181 [2]
Signed-off-by: Coiby Xu <coxu@redhat.com>
Suggested-by: Will Deacon <will@kernel.org>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Arnaud Lefebvre <arnaud.lefebvre@clever-cloud.com>
Cc: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Cc: Dave Young <dyoung@redhat.com>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Sourabh Jain <sourabhjain@linux.ibm.com>
Cc: Thomas Staudt <tstaudt@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>