Kernel: Mark sys$fcntl as not needing the big lock

This syscall operates on the file descriptor table, and on individual
open file descriptions. Both of those are already protected by scoped
locking mechanisms.

Kernel/API/Syscall.h

@@ -77,7 +77,7 @@ enum class NeedsBigProcessLock {
     S(fchdir, NeedsBigProcessLock::No)                      \
     S(fchmod, NeedsBigProcessLock::No)                      \
     S(fchown, NeedsBigProcessLock::No)                      \
-    S(fcntl, NeedsBigProcessLock::Yes)                      \
+    S(fcntl, NeedsBigProcessLock::No)                       \
     S(fork, NeedsBigProcessLock::Yes)                       \
     S(fstat, NeedsBigProcessLock::No)                       \
     S(fstatvfs, NeedsBigProcessLock::No)                    \

Kernel/Syscalls/fcntl.cpp

@@ -12,7 +12,7 @@ namespace Kernel {
 
 ErrorOr<FlatPtr> Process::sys$fcntl(int fd, int cmd, uintptr_t arg)
 {
-    VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this);
+    VERIFY_NO_PROCESS_BIG_LOCK(this);
     TRY(require_promise(Pledge::stdio));
     dbgln_if(IO_DEBUG, "sys$fcntl: fd={}, cmd={}, arg={}", fd, cmd, arg);
     auto description = TRY(open_file_description(fd));