staging: csr: remove func_exit macro

this macro is used for debugging purposes,

it actually defined as

if (unifi_debug >= 5) {
	printk("unifi: <= %s\n", __FUNCTION__);
}

which produces too many of those prints if the unifi_debug is >=5.
remove these calls and the macro itself altogether

Signed-off-by: Devendra Naga <devendra.aaru@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>