staging: vt6656: s_vGenerateTxParameter pvRrvTime should never be NULL

If pvRrvTime is NULL the whole structure is NULL, so
remove if statements and consolidate to single return.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>