powerpc/fadump: Update comment about offset where fadump is reserved

With commit f6e6bedb7731 ("powerpc/fadump: Reserve memory at an offset
closer to bottom of RAM"), memory for fadump is no longer reserved at
the top of RAM. But there are still a few places which say so. Change
them appropriately.

Signed-off-by: Hari Bathini <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>

Documentation/powerpc/firmware-assisted-dump.txt

···
          boot successfully. For syntax of crashkernel= parameter,
          refer to Documentation/kdump/kdump.txt. If any offset is
          provided in crashkernel= parameter, it will be ignored
-         as fadump reserves memory at end of RAM for boot memory
-         dump preservation in case of a crash.
+         as fadump uses a predefined offset to reserve memory
+         for boot memory dump preservation in case of a crash.
 
 -- After the low memory (boot memory) area has been saved, the
    firmware will reset PCI and other hardware state.  It will

arch/powerpc/kernel/fadump.c

···
 
 	/*
 	 * Check if the size is specified through crashkernel= cmdline
-	 * option. If yes, then use that but ignore base as fadump
-	 * reserves memory at end of RAM.
+	 * option. If yes, then use that but ignore base as fadump reserves
+	 * memory at a predefined offset.
 	 */
 	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
 				&size, &base);