mfd: rohm-bd71828: Use standard file header format

The MFD subsystem uses C-style comments also in the 'file header'
section. Switch to this for the sake of the consistency. The header
content is not changed.

Suggested-by: Lee Jones <lee@kernel.org>
Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
Link: https://patch.msgid.link/3cc6176eee16a7edc75c94d967a1de67be400e97.1765804226.git.mazziesaccount@gmail.com
Signed-off-by: Lee Jones <lee@kernel.org>