staging: most: use preferred kzalloc parameters

This patch uses the preferred call to kzalloc. It replaces
kzalloc(sizeof(struct aim_fh)...) by kzalloc(sizeof(*fh)...).

Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>