staging: r8188eu: Remove _func_enter and _func_exit macros

These debugging macros are seldom used for debugging once the driver
is working. If routine tracing is needed, it can be added on an
individual basis.

In a few cases, removal of the exit macro left a bare label. In these
cases, a go to that label was replaced by a return.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>