powerpc/40x: Remove IBM405 Erratum #51

This erratum was for IBM 403GCX, 405EP and STB03xxx which are
now gone.

Remove this erratum.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1b6c9916514ef3e084bba57925ad9eb444627566.1590079969.git.christophe.leroy@csgroup.eu

arch/powerpc/kernel/head_40x.S

@@ -426,13 +426,7 @@ _ENTRY(saved_ksp_limit)
 	EXCEPTION(0x1400, Trap_14, unknown_exception, EXC_XFER_STD)
 	EXCEPTION(0x1500, Trap_15, unknown_exception, EXC_XFER_STD)
 	EXCEPTION(0x1600, Trap_16, unknown_exception, EXC_XFER_STD)
-#ifdef CONFIG_IBM405_ERR51
-	/* 405GP errata 51 */
-	START_EXCEPTION(0x1700, Trap_17)
-	b DTLBMiss
-#else
 	EXCEPTION(0x1700, Trap_17, unknown_exception, EXC_XFER_STD)
-#endif
 	EXCEPTION(0x1800, Trap_18, unknown_exception, EXC_XFER_STD)
 	EXCEPTION(0x1900, Trap_19, unknown_exception, EXC_XFER_STD)
 	EXCEPTION(0x1A00, Trap_1A, unknown_exception, EXC_XFER_STD)

arch/powerpc/platforms/40x/Kconfig

@@ -75,10 +75,6 @@ config PPC4xx_GPIO
 config IBM405_ERR77
 	bool
 
-# All 40x-based cores, up until the 405GPR and 405EP have this errata.
-config IBM405_ERR51
-	bool
-
 config APM8018X
 	bool "APM8018X"
 	depends on 40x