IB/hfi1: Fix double QSFP resource acquire on cache refresh

The function refresh_qsfp_cache() acquires the i2c chain resource,
but one caller already holds the resource.  Change the acquire so
all calls to refresh_qsfp_cache() are covered by the acquire and
remove the acquire within refresh_qsfp_cache().

Reviewed-by: Easwar Hariharan <easwar.hariharan@intel.com>
Signed-off-by: Dean Luick <dean.luick@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>