Welcome in the forum!
The trailing 'u' after an integer constant advises the compiler to treat the number as an "unsigned" item. To use this qualifier after every constant (if needed or not) conforms to the "MISRA" coding rules which imho do not make readability easier. Companies as Cypress are bound to follow these rules. So the above lies could have been written as
line 220 keyboard_data = 0; /* Set up keyboard data*/
line 221 keyboard_data = 0; /* Set up keyboard data*/
which is more the usual C-language style.