staging: vt6655: Replace unused return value of vt6655_get_current_tsf

Replace unused return value with u64 to increase readability,
reduce address and dereference operators and omit pqwCurrTSF that
uses CamelCase which is not accepted by checkpatch.pl

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/62c83d78627196ec0ce2f5a562cb080a1c87a05a.1651435890.git.philipp.g.hortmann@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>