i2c: Let i2c-core.h include <linux/i2c.h>

i2c: Let i2c-core.h include <linux/i2c.h>

The subsystem private header i2c-core.h uses several symbols defined in
<linux/i2c.h>, e.g. struct i2c_board_info and i2c_lock_bus()). This
doesn't pose a problem in practise because all files including
"i2c-core.h" also include <linux/i2c.h>.

To make this more robust add an include statement for <linux/i2c.h>
making the header self-contained.

Acked-by: Danilo Krummrich <dakr@kernel.org>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://patch.msgid.link/46aa85ab3dc4e63bfb5bd8ff1fd212a3d0e31f58.1782808461.git.u.kleine-koenig@baylibre.com
Signed-off-by: Uwe Kleine-König (The Capable Hub) <u.kleine-koenig@baylibre.com>