MIPS: Require O32 FP64 support for MIPS64 with O32 compat

MIPS32r6 code requires FP64 (ie. FR=1) support. Building a kernel with
support for MIPS32r6 binaries but without support for O32 with FP64 is
therefore a problem which can lead to incorrectly executed userland.

CONFIG_MIPS_O32_FP64_SUPPORT is already selected when the kernel is
configured for MIPS32r6, but not when the kernel is configured for
MIPS64r6 with O32 compat support. Select CONFIG_MIPS_O32_FP64_SUPPORT in
such configurations to prevent building kernels which execute MIPS32r6
userland incorrectly.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Cc: <stable@vger.kernel.org> # v4.0-
Cc: linux-mips@linux-mips.org
Cc: Matthew Fortune <matthew.fortune@imgtec.com>
Cc: stable@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/10674/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -1427,6 +1427,7 @@ config CPU_MIPS64_R6
 	select CPU_SUPPORTS_HIGHMEM
 	select CPU_SUPPORTS_MSA
 	select GENERIC_CSUM
+	select MIPS_O32_FP64_SUPPORT if MIPS32_O32
 	help
 	  Choose this option to build a kernel for release 6 or later of the
 	  MIPS64 architecture.  New MIPS processors, starting with the Warrior