powerpc/cputable: Remove __machine_check_early_realmode_p{7/8/9} prototypes

__machine_check_early_realmode_p{7/8/9} are already in mce.h
which is included. Remove them from cputable.c

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/b77fc0f90e3a9c065324cbff549b718ccf0809f8.1663606875.git.christophe.leroy@csgroup.eu