powerpc: reword ARCH_FORCE_MAX_ORDER prompt and help text

The prompt and help text of ARCH_FORCE_MAX_ORDER are not even close to
describe this configuration option.

Update both to actually describe what this option does.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Mike Rapoport (IBM) <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
Reviewed-by: Zi Yan <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Christophe Leroy <[email protected]>
Cc: David Miller <[email protected]>
Cc: Dinh Nguyen <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Guo Ren <[email protected]>
Cc: John Paul Adrian Glaubitz <[email protected]>
Cc: Max Filippov <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Rich Felker <[email protected]>
Cc: "Russell King (Oracle)" <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Yoshinori Sato <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: rppt

arch/powerpc/Kconfig

@@ -896,7 +896,7 @@ config DATA_SHIFT
 	  8M pages will be pinned.
 
 config ARCH_FORCE_MAX_ORDER
-	int "Maximum zone order"
+	int "Order of maximal physically contiguous allocations"
 	range 7 8 if PPC64 && PPC_64K_PAGES
 	default "8" if PPC64 && PPC_64K_PAGES
 	range 12 12 if PPC64 && !PPC_64K_PAGES
@@ -910,17 +910,19 @@ config ARCH_FORCE_MAX_ORDER
 	range 10 63
 	default "10"
 	help
-	  The kernel memory allocator divides physically contiguous memory
-	  blocks into "zones", where each zone is a power of two number of
-	  pages.  This option selects the largest power of two that the kernel
-	  keeps in the memory allocator.  If you need to allocate very large
-	  blocks of physically contiguous memory, then you may need to
-	  increase this value.
+	  The kernel page allocator limits the size of maximal physically
+	  contiguous allocations. The limit is called MAX_ORDER and it
+	  defines the maximal power of two of number of pages that can be
+	  allocated as a single contiguous block. This option allows
+	  overriding the default setting when ability to allocate very
+	  large blocks of physically contiguous memory is required.
 
 	  The page size is not necessarily 4KB.  For example, on 64-bit
 	  systems, 64KB pages can be enabled via CONFIG_PPC_64K_PAGES.  Keep
 	  this in mind when choosing a value for this option.
 
+	  Don't change if unsure.
+
 config PPC_SUBPAGE_PROT
 	bool "Support setting protections for 4k subpages (subpage_prot syscall)"
 	default n