scripts/get_abi.pl: add a handler for invalid "where" tag

The ABI README file doesn't provide any meaning for a Where:
tag. Yet, a few ABI symbols use it. So, make the parser
handle it, emitting a warning.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>