staging: rtl8712: replace kmalloc(..., sizeof(T))

As suggested by Andy Shevchenko on driverdev-devel, replace
v = ... sizeof(struct type_of_v) -> sizeof(*v)

Based on a cocci patch along the lines of

@@
type T;
expression E;
identifier V;
@@

T *V;
...
- V = kmalloc(sizeof(T), E);
+ V = kmalloc(sizeof(*V), E);

@@
type T;
expression E;
identifier V;
@@

T *V;
...
- V = kzalloc(sizeof(T), E);
+ V = kzalloc(sizeof(*V), E);

Signed-off-by: Vitaly Osipov <vitaly.osipov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>