execsnoop: fix the prototype for kprobe__sys_execve
execsnoop: fix the prototype for kprobe__sys_execve

For sys_execve() the type of filename parameter should be
"const char __user *" instead of "struct filename *".

The fix doesn't imply any functional change.

tuxology/bcc,iovisor/bcc,brendangregg/bcc,mcaleavya/bcc,brendangregg/bcc,iovisor/bcc,iovisor/bcc,brendangregg/bcc,mcaleavya/bcc,iovisor/bcc,brendangregg/bcc,tuxology/bcc,mcaleavya/bcc,tuxology/bcc,tuxology/bcc,tuxology/bcc,mcaleavya/bcc,brendangregg/bcc,iovisor/bcc,mcaleavya/bcc