m32r: add __ucmpdi2 to fix build failure

We are having build failure with m32r and the error message being:

  ERROR: "__ucmpdi2" [lib/842/842_decompress.ko] undefined!
  ERROR: "__ucmpdi2" [fs/btrfs/btrfs.ko] undefined!
  ERROR: "__ucmpdi2" [drivers/scsi/sd_mod.ko] undefined!
  ERROR: "__ucmpdi2" [drivers/media/i2c/adv7842.ko] undefined!
  ERROR: "__ucmpdi2" [drivers/md/bcache/bcache.ko] undefined!
  ERROR: "__ucmpdi2" [drivers/iio/imu/inv_mpu6050/inv-mpu6050.ko] undefined!

__ucmpdi2 is introduced to m32r architecture taking example from other
architectures like h8300, microblaze, mips.

Link: http://lkml.kernel.org/r/1465509213-4280-1-git-send-email-sudipm.mukherjee@gmail.com
Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/m32r/lib/libgcc.h

@@ -0,0 +1,23 @@
+#ifndef __ASM_LIBGCC_H
+#define __ASM_LIBGCC_H
+
+#include <asm/byteorder.h>
+
+#ifdef __BIG_ENDIAN
+struct DWstruct {
+	int high, low;
+};
+#elif defined(__LITTLE_ENDIAN)
+struct DWstruct {
+	int low, high;
+};
+#else
+#error I feel sick.
+#endif
+
+typedef union {
+	struct DWstruct s;
+	long long ll;
+} DWunion;
+
+#endif /* __ASM_LIBGCC_H */