comms/rtl-sdr: Update 2.0.2 => 2.0.3

• Switch MASTER_SITES to static tarball from official site
• Clarify WWW; add 2-nd WWW for source code repository
• Add LICENSE_FILE
• Use localbase
• Pet portclippy(1) and portfmt(1)

Approved by: martymac@ (maintainer)
Approved by: db@, yuri@ (Mentors, implicit)
Differential Revision: https://reviews.freebsd.org/D58850