checksyscalls: fix "here document" handling

checksyscalls: fix "here document" handling

"echo" doesn't read from stdin, therefore the checksyscalls script didn't
warn about not implemented system calls anymore since 29dc54c6
("checksyscalls: Use arch/x86/syscalls/syscall_32.tbl as source").

Use "cat" instead of "echo" which handles this correctly.

Signed-off-by: Heiko Carstens <[email protected]>
Cc: Michal Marek <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Cyrill Gorcunov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>