header: Add BITS_PER_TYPE()

Upstream commit: a231817c01bda4020632d5c62429e1bdf93f73e5

BITS_PER_TYPE was moved in the upstream kernel in commit 9144d75e22ca
("include/linux/bitops.h: introduce BITS_PER_TYPE") in kernel 4.19 and
is now used by the ath10k driver.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
diff --git a/backport/backport-include/linux/bitops.h b/backport/backport-include/linux/bitops.h
index 86360d0..17bd813 100644
--- a/backport/backport-include/linux/bitops.h
+++ b/backport/backport-include/linux/bitops.h
@@ -20,4 +20,8 @@
 #define BIT_ULL(nr) (1ULL << (nr))
 #endif
 
+#ifndef BITS_PER_TYPE
+#define BITS_PER_TYPE(type) (sizeof(type) * BITS_PER_BYTE)
+#endif
+
 #endif /* __BACKPORT_BITOPS_H */