staging: rtl8188eu: core: Use sizeof(*p) instead of sizeof(struct P) for memory allocation

Use sizeof(*ptr) instead of sizeof(ptr_type) makes memory
allocation easy in case the type of pointer changes.
Fix all checkpatch reported issues for "CHECK: Prefer
kzalloc(sizeof(*<p>)...) over kzalloc(sizeof(struct <P>)...)".

Signed-off-by: Mamta Shukla <mamtashukla555@gmail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>