i2c-algo-pcf: Discard the mdelay data struct member

Just as i2c-algo-bit, i2c-algo-pcf has an unused mdelay struct member,
which we can get rid of to spare some code and memory.
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>