MAINTAINERS: adjust to removing i2c designware platform data

Commit 5a517b5b

 ("i2c: designware: Get rid of legacy platform data")
removes ./include/linux/platform_data/i2c-designware.h, but misses to
adjust the SYNOPSYS DESIGNWARE I2C DRIVER section in MAINTAINERS.

Hence, ./scripts/get_maintainer.pl --self-test=patterns complains:

  warning: no file matches F: include/linux/platform_data/i2c-designware.h

Remove the file entry to this removed file as well.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>