[IA64] Fix build error: conflicting types for ‘sys_execve’

arch/ia64/kernel/process.c:636: error: conflicting types for ‘sys_execve’

commit d7627467
Make do_execve() take a const filename pointer

Missed the declaration of sys_execve in the ia64 asm/unistd.h (perhaps
because there is no reason for it to be there ... it might be a left over
from the COMPAT code?). Just delete the conflicting version.
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/include/asm/unistd.h

@@ -356,8 +356,6 @@ asmlinkage unsigned long sys_mmap2(
 				int fd, long pgoff);
 struct pt_regs;
 struct sigaction;
-long sys_execve(const char __user *filename, char __user * __user *argv,
-			   char __user * __user *envp, struct pt_regs *regs);
 asmlinkage long sys_ia64_pipe(void);
 asmlinkage long sys_rt_sigaction(int sig,
 				 const struct sigaction __user *act,