rtl8xxxu: Use size of source pointer when copying efuse data

Some newer chips have more channel groups in their efuse parameter
tables, so use the size of the source, rather than the destination
when copying them out. This avoids copying garbage when increasing the
common array sizes.

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>