drm/amdgpu: Fix a bug for input with double sscanf

Remove double-sscanf to scan for %llu and 0x%llx,
as that is not going to work!

The %llu will consume the "0" in "0x" of your
input, and the hex value you think you're entering
will always be 0. That is, a valid hex value can
never be consumed.

On the other hand, just entering a hex number
without leading 0x will either be scanned as a
string and not match, for instance FAB123, or
the leading decimal portion is scanned as the
%llu, for instance 123FAB will be scanned as 123,
which is not correct.

Thus remove the first %llu scan and leave only the
%llx scan, removing the leading 0x since %llx can
scan either.

Addresses are usually always hex values, so this
suffices.

Cc: Alexander Deucher <Alexander.Deucher@amd.com>
Cc: Xinhui Pan <xinhui.pan@amd.com>
Cc: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>