powerpc/time: Remove get_tbu()

get_tbu() is redundant with mftbu() and is not used anymore.

Remove it.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1746e2d11ea90c3f45877e1fcc6c79ce96cf6b98.1601556145.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/time.h

@@ -49,11 +49,6 @@ static inline unsigned long get_tbl(void)
 {
 	return mftb();
 }
-
-static inline unsigned int get_tbu(void)
-{
-	return mftbu();
-}
 #endif /* !CONFIG_PPC64 */
 
 static inline u64 get_vtb(void)