arm64: kaslr: Use standard early random function

Commit 58552408 ("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: 58552408 ("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>