parisc: add missing export of __cmpxchg_u8()

__cmpxchg_u8() had been added (initially) for the sake of
drivers/phy/ti/phy-tusb1210.c; the thing is, that drivers is
modular, so we need an export

Fixes: b344d6a8 "parisc: add support for cmpxchg on u8 pointers"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

arch/parisc/kernel/parisc_ksyms.c

@@ -22,6 +22,7 @@ EXPORT_SYMBOL(memset);
 #include <linux/atomic.h>
 EXPORT_SYMBOL(__xchg8);
 EXPORT_SYMBOL(__xchg32);
+EXPORT_SYMBOL(__cmpxchg_u8);
 EXPORT_SYMBOL(__cmpxchg_u32);
 EXPORT_SYMBOL(__cmpxchg_u64);
 #ifdef CONFIG_SMP