powerpc/cell: Remove dead extern declaration for spu_priv1_beat_ops

spu_priv1_beat_ops were removed in commit bf4981a ("powerpc: Remove
the celleb support"), remove the unneeded extern.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20241112114805.453894-1-mpe@ellerman.id.au

Author: mpe

arch/powerpc/include/asm/spu_priv1.h

@@ -216,7 +216,6 @@ spu_disable_spu (struct spu_context *ctx)
  */
 
 extern const struct spu_priv1_ops spu_priv1_mmio_ops;
-extern const struct spu_priv1_ops spu_priv1_beat_ops;
 
 extern const struct spu_management_ops spu_management_of_ops;