lib/mpi/longlong.h: fix building with 32-bit x86

lib/mpi/longlong.h: fix building with 32-bit x86

The mpi library contains some rather old inline assembly statements that
produce a lot of warnings for 32-bit x86, such as:

  lib/mpi/mpih-div.c:76:16: error: invalid use of a cast in a inline asm context requiring an l-value: remove the cast or build with -fheinous-gnu-extensions
                                  udiv_qrnnd(qp[i], n1, n1, np[i], d);
                                  ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
  lib/mpi/longlong.h:423:20: note: expanded from macro 'udiv_qrnnd'
          : "=a" ((USItype)(q)), \
                  ~~~~~~~~~~^~

There is no point in doing a type cast for the output of an inline
assembler statement, so just remove the cast here, as we have done for
other architectures in the past.

See also dea632cadd12 ("lib/mpi: fix build with clang").

Link: http://lkml.kernel.org/r/20190712090740.340186-1-arnd@arndb.de
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>