multimedia/motion: unbreak the port's build against MYSQL option

This is not a 100% correct fix, more of a mitigation: ``pkg-config
--cflags mysqlclient'' fails with default OpenSSL, and thus MySQL
header files could be be found:

Package openssl was not found in the pkg-config search path.
Perhaps you should add the directory containing `openssl.pc'
to the PKG_CONFIG_PATH environment variable
Package 'openssl', required by 'mysqlclient', not found

The configure script makes several other bogus (at least in FreeBSD
context) assumptions, but those could be fixed in a separate commit.

Drop no longer supported options from the CONFIGURE_ARGS while here.