staging: rtl8192u: ieee80211: Remove msleep_interruptible_rsl Macro

Remove driver specific macro msleep_interruptible_rsl as it has been
replaced by a direct call to msleep_interruptible in the single
instance referencing it.

Signed-off-by: Amitoj Kaur Chawla <amitoj1606@gmail.com>
Reviewed-by: Vaishali Thakkar <vaishali.thakkar@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>