char: misc: Remove redundant forward declarations

Header miscdevice.h includes linux/device.h which has definations for
below two forward declarations directly or indirectly:

struct device;
struct attribute_group;

Remove these redundant forward declarations from miscdevice.h

Signed-off-by: Zijun Hu <zijun.hu@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250620-fix_mischar-v1-1-6c2716bbf1fa@oss.qualcomm.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>