gdb: fix build of gdbserver on m68k/coldfire

gdb: fix build of gdbserver on m68k/coldfire

This commit adds a small patch to gdb that fixes the build of gdbserver
on m68k/coldfire:

../nat/linux-ptrace.c: In function 'linux_fork_to_function':
../nat/linux-ptrace.c:282:19: warning: implicit declaration of function 'clone' [-Wimplicit-function-declaration]
       child_pid = clone (function, child_stack + STACK_SIZE,
                   ^
../nat/linux-ptrace.c:283:5: error: 'CLONE_VM' undeclared (first use in this function)
     CLONE_VM | SIGCHLD, child_stack + STACK_SIZE * 2);
     ^
../nat/linux-ptrace.c:283:5: note: each undeclared identifier is reported only once for each function it appears in

Thanks to Waldemar for pointing out the patch fixing this issue.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
---
Changes since v2:
 - None
Changes since v1:
 - New patch in the series