media: pci: tw5864: avoid usage of some characters

There are several comments on this driver using those chars:

	- U+2013 ('–'): EN DASH
	- U+2018 ('‘'): LEFT SINGLE QUOTATION MARK
	- U+2019 ('’'): RIGHT SINGLE QUOTATION MARK

They probably came from cut-and-pasting some texts found
elsewhere.

While there's nothing wrong on having those on comments in
C, it is better to use ASCII chars for those specific cases,
as the current variant doesn't really add any value.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>