fix syntax error and style

student-distrib/Proc.c

student-distrib/Proc.h

student-distrib/bootimg

student-distrib/kernel.c

student-distrib/keyboard.c

student-distrib/keyboard.h

student-distrib/mp3.img

student-distrib/paging.c

student-distrib/paging.h

student-distrib/pit.c

student-distrib/pit.h

student-distrib/proc.c

student-distrib/scheduler.c

student-distrib/scheduler.h

student-distrib/syscall.c

student-distrib/syscall.h

student-distrib/syscall_asm.S

student-distrib/terminal.c

student-distrib/terminal.h

student-distrib/types.h