V4L/DVB (7792): ivtv: correct misspelled "HIMEM4G" to "HIGHMEM4G" in error message

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>