staging: gdm724x: correct kzalloc/kmalloc sizeof argument

This patch converts sizeof(TYPE) to sizeof(VAR) when used as
a kzalloc/kmaloc argument.

Signed-off-by: Ioana Ciornei <ciorneiioana@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>