All 'pid_t' were changed to '__kernel_pid_t' in a previous commit:
make exported headers use strict posix types

    A number of standard posix types are used in exported headers,
    which is not allowed if __STRICT_KERNEL_NAMES is defined. In order
    to get rid of the non-__STRICT_KERNEL_NAMES part and to make sane
    headers the default, we have to change them all to safe types.

but a later change introduced 'pid_t' again:
    fcntl: add F_[SG]ETOWN_EX

This makes asm-generic/fcntl.h d use strict posix types again.
Signed-off-by: Lucian Adrian Grijincu <lucian.grijincu@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>