powerpc/book3e: get rid of #include <generated/compile.h>

You cannot include <generated/compile.h> here because it is generated
in init/Makefile but there is no guarantee that it happens before
arch/powerpc/mm/nohash/kaslr_booke.c is compiled for parallel builds.

The places where you can reliably include <generated/compile.h> are:

  - init/          (because init/Makefile can specify the dependency)
  - arch/*/boot/   (because it is compiled after vmlinux)

Commit f231e433 ("hexagon: get rid of #include <generated/compile.h>")
fixed the last breakage at that time, but powerpc re-added this.

<generated/compile.h> was unneeded because 'build_str' is almost the
same as 'linux_banner' defined in init/version.c

Let's copy the solution from MIPS.
(get_random_boot() in arch/mips/kernel/relocate.c)

Fixes: 6a38ea1d ("powerpc/fsl_booke/32: randomize the kernel image offset")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Scott Wood <oss@buserror.net>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220604085050.4078927-1-masahiroy@kernel.org

arch/powerpc/mm/nohash/kaslr_booke.c

@@ -19,7 +19,6 @@
 #include <asm/cacheflush.h>
 #include <asm/kdump.h>
 #include <mm/mmu_decl.h>
-#include <generated/compile.h>
 #include <generated/utsrelease.h>
 
 struct regions {
@@ -37,10 +36,6 @@ struct regions {
 	int reserved_mem_size_cells;
 };
 
-/* Simplified build-specific string for starting entropy. */
-static const char build_str[] = UTS_RELEASE " (" LINUX_COMPILE_BY "@"
-		LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION;
-
 struct regions __initdata regions;
 
 static __init void kaslr_get_cmdline(void *fdt)
@@ -71,7 +66,8 @@ static unsigned long __init get_boot_seed(void *fdt)
 {
 	unsigned long hash = 0;
 
-	hash = rotate_xor(hash, build_str, sizeof(build_str));
+	/* build-specific string for starting entropy. */
+	hash = rotate_xor(hash, linux_banner, strlen(linux_banner));
 	hash = rotate_xor(hash, fdt, fdt_totalsize(fdt));
 
 	return hash;