Building perf for MIPS failed after 9f79b8b7 ("uapi: simplify
__ARCH_FLOCK{,64}_PAD a little") with the following error:

  CC
/home/fainelli/work/buildroot/output/bmips/build/linux-custom/tools/perf/trace/beauty/fcntl.o
In file included from
../../../../host/mipsel-buildroot-linux-gnu/sysroot/usr/include/asm/fcntl.h:77,
                 from ../include/uapi/linux/fcntl.h:5,
                 from trace/beauty/fcntl.c:10:
../include/uapi/asm-generic/fcntl.h:188:8: error: redefinition of
'struct flock'
 struct flock {
        ^~~~~
In file included from ../include/uapi/linux/fcntl.h:5,
                 from trace/beauty/fcntl.c:10:
../../../../host/mipsel-buildroot-linux-gnu/sysroot/usr/include/asm/fcntl.h:63:8:
note: originally defined here
 struct flock {
        ^~~~~

This is due to the local copy under
tools/include/uapi/asm-generic/fcntl.h including the toolchain's kernel
headers which already define 'struct flock' and define
HAVE_ARCH_STRUCT_FLOCK to future inclusions make a decision as to
whether re-defining 'struct flock' is appropriate or not.

Make sure what do not re-define 'struct flock'
when HAVE_ARCH_STRUCT_FLOCK is already defined.

Fixes: 9f79b8b7 ("uapi: simplify __ARCH_FLOCK{,64}_PAD a little")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
[arnd: sync with include/uapi/asm-generic/fcntl.h as well]
Signed-off-by: Arnd Bergmann <arnd@arndb.de>