powerpc/64s: Replace CONFIG_PPC_STD_MMU_64 with CONFIG_PPC_BOOK3S_64

CONFIG_PPC_STD_MMU_64 indicates support for the "standard" powerpc MMU
on 64-bit CPUs. The "standard" MMU refers to the hash page table MMU
found in "server" processors, from IBM mainly.

Currently CONFIG_PPC_STD_MMU_64 is == CONFIG_PPC_BOOK3S_64. While it's
annoying to have two symbols that always have the same value, it's not
quite annoying enough to bother removing one.

However with the arrival of Power9, we now have the situation where
CONFIG_PPC_STD_MMU_64 is enabled, but the kernel is running using the
Radix MMU - *not* the "standard" MMU. So it is now actively confusing
to use it, because it implies that code is disabled or inactive when
the Radix MMU is in use, however that is not necessarily true.

So s/CONFIG_PPC_STD_MMU_64/CONFIG_PPC_BOOK3S_64/, and do some minor
formatting updates of some of the affected lines.

This will be a pain for backports, but c'est la vie.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/Kconfig

@@ -334,7 +334,7 @@ config PPC_OF_PLATFORM_PCI
 	default n
 
 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
-	depends on PPC32 || PPC_STD_MMU_64
+	depends on PPC32 || PPC_BOOK3S_64
 	def_bool y
 
 config ARCH_SUPPORTS_UPROBES
@@ -721,7 +721,7 @@ config PPC_16K_PAGES
 
 config PPC_64K_PAGES
 	bool "64k page size"
-	depends on !PPC_FSL_BOOK3E && (44x || PPC_STD_MMU_64 || PPC_BOOK3E_64)
+	depends on !PPC_FSL_BOOK3E && (44x || PPC_BOOK3S_64 || PPC_BOOK3E_64)
 	select HAVE_ARCH_SOFT_DIRTY if PPC_BOOK3S_64
 
 config PPC_256K_PAGES
@@ -780,7 +780,7 @@ config FORCE_MAX_ZONEORDER
 
 config PPC_SUBPAGE_PROT
 	bool "Support setting protections for 4k subpages"
-	depends on PPC_STD_MMU_64 && PPC_64K_PAGES
+	depends on PPC_BOOK3S_64 && PPC_64K_PAGES
 	help
 	  This option adds support for a system call to allow user programs
 	  to set access permissions (read/write, readonly, or no access)