powerpc: define get_cycles macro for arch-override

PowerPC defines a get_cycles() function, but it does not do the usual
`#define get_cycles get_cycles` dance, making it impossible for generic
code to see if an arch-specific function was defined. While the
get_cycles() ifdef is not currently used, the following timekeeping
patch in this series will depend on the macro existing (or not existing)
when defining random_get_entropy().

Cc: Thomas Gleixner <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Paul Mackerras <[email protected]>
Acked-by: Michael Ellerman <[email protected]>
Signed-off-by: Jason A. Donenfeld <[email protected]>

arch/powerpc/include/asm/timex.h

@@ -19,6 +19,7 @@ static inline cycles_t get_cycles(void)
 {
 	return mftb();
 }
+#define get_cycles get_cycles
 
 #endif	/* __KERNEL__ */
 #endif	/* _ASM_POWERPC_TIMEX_H */