arm64: kaslr: Use standard early random function

Commit 585524081e ("random: random.h should include archrandom.h, not
the other way around") tries to fix a problem with recursive inclusion
of linux/random.h and arch/archrandom.h for arm64.  Unfortunately, this
results in the following compile error if ARCH_RANDOM is disabled.

  arch/arm64/kernel/kaslr.c: In function 'kaslr_early_init':
  arch/arm64/kernel/kaslr.c:128:6: error: implicit declaration of function '__early_cpu_has_rndr'; did you mean '__early_pfn_to_nid'? [-Werror=implicit-function-declaration]
    if (__early_cpu_has_rndr()) {
        ^~~~~~~~~~~~~~~~~~~~
        __early_pfn_to_nid
  arch/arm64/kernel/kaslr.c:131:7: error: implicit declaration of function '__arm64_rndr' [-Werror=implicit-function-declaration]
     if (__arm64_rndr(&raw))
         ^~~~~~~~~~~~

The problem is that arch/archrandom.h is only included from
linux/random.h if ARCH_RANDOM is enabled.  If not, __arm64_rndr() and
__early_cpu_has_rndr() are undeclared, causing the problem.

Use arch_get_random_seed_long_early() instead of arm64 specific
functions to solve the problem.

Reported-by: Qian Cai <cai@lca.pw>
Fixes: 585524081e ("random: random.h should include archrandom.h, not the other way around")
Cc: Qian Cai <cai@lca.pw>
Cc: Mark Brown <broonie@kernel.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Tested-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/arm64/kernel/kaslr.c

@@ -84,6 +84,7 @@ u64 __init kaslr_early_init(u64 dt_phys)
 	void *fdt;
 	u64 seed, offset, mask, module_range;
 	const u8 *cmdline, *str;
+	unsigned long raw;
 	int size;
 
 	/*
@@ -122,15 +123,12 @@ u64 __init kaslr_early_init(u64 dt_phys)
 	}
 
 	/*
-	 * Mix in any entropy obtainable architecturally, open coded
+	 * Mix in any entropy obtainable architecturally if enabled
-	 * since this runs extremely early.
+	 * and supported.
 	 */
-	if (__early_cpu_has_rndr()) {
-		unsigned long raw;
 
-		if (__arm64_rndr(&raw))
+	if (arch_get_random_seed_long_early(&raw))
-			seed ^= raw;
+		seed ^= raw;
-	}
 
 	if (!seed) {
 		kaslr_status = KASLR_DISABLED_NO_SEED;