bus: fsl-mc: Use strscpy() instead of strscpy_pad()

bus: fsl-mc: Use strscpy() instead of strscpy_pad()

Both destination buffers are already zero-initialized, making strscpy()
sufficient for safely copying 'obj_type'. The additional NUL-padding
performed by strscpy_pad() is unnecessary.

If the destination buffer has a fixed length, strscpy() automatically
determines its size using sizeof() when the argument is omitted. This
makes the explicit size arguments unnecessary.

No functional changes intended.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Reviewed-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Link: https://lore.kernel.org/r/20250429104149.66334-1-thorsten.blum@linux.dev
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>