Fix the missing error code when register_chrdev() failed. The report is from Smatch: Smatch failed: 1 warning(s), 0 error(s) /home/runner/work/lkmpg/lkmpg/examples/vinput.c:372 vinput_init() warn: missing error code 'err'
The description of the attribute was added in sysfs section and referenced in vinput section. In vinput section, just described the class_attribute and some macros about sysfs class. Add file name at vinput-related examples begin.
Add the new section of input device driver, vinput[1]. Also, update the Acknowledgements. [1] https://github.com/sysprog21/vinput
