misc: amd-sbi: Explicitly clear in/out arg "mb_in_out"

misc: amd-sbi: Explicitly clear in/out arg "mb_in_out"

- New AMD processor will support different input/output for same command.
- In some scenarios the input value is not cleared, which will be added to
  output before reporting the data.
- Clearing input explicitly will be a cleaner and safer approach.

Reviewed-by: Naveen Krishna Chatradhi <naveenkrishna.chatradhi@amd.com>
Signed-off-by: Akshay Gupta <akshay.gupta@amd.com>
Link: https://lore.kernel.org/r/20250716110729.2193725-3-akshay.gupta@amd.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>