xtensa: use fallback for random_get_entropy() instead of zero

stable inclusion
from stable-v5.10.119
commit ffcfdd5de9d0287da52522fbcd1bbba52c81b3ef
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5L6BB

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ffcfdd5de9d0287da52522fbcd1bbba52c81b3ef

--------------------------------

commit e10e2f58 upstream.

In the event that random_get_entropy() can't access a cycle counter or
similar, falling back to returning 0 is really not the best we can do.
Instead, at least calling random_get_entropy_fallback() would be
preferable, because that always needs to return _something_, even
falling back to jiffies eventually. It's not as though
random_get_entropy_fallback() is super high precision or guaranteed to
be entropic, but basically anything that's not zero all the time is
better than returning zero all the time.

This is accomplished by just including the asm-generic code like on
other architectures, which means we can get rid of the empty stub
function here.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Acked-by: NMax Filippov <jcmvbkbc@gmail.com>
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

arch/xtensa/include/asm/timex.h

@@ -29,10 +29,6 @@
 
 extern unsigned long ccount_freq;
 
-typedef unsigned long long cycles_t;
-
-#define get_cycles()	(0)
-
 void local_timer_setup(unsigned cpu);
 
 /*
@@ -59,4 +55,6 @@ static inline void set_linux_timer (unsigned long ccompare)
 	xtensa_set_sr(ccompare, SREG_CCOMPARE + LINUX_TIMER);
 }
 
+#include <asm-generic/timex.h>
+
 #endif	/* _XTENSA_TIMEX_H */