Since the commit 819e50e2 ("arm64: Add ftrace support"),
HAVE_FUNCTION_GRAPH_TRACER has always been enabled. Although a subsequent
commit 36469703 ("arm64: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL")
redundantly added check on HAVE_FUNCTION_GRAPH_TRACER, while enabling the
config HAVE_FUNCTION_GRAPH_RETVAL. Let's just drop this redundant check.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
CC: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20240716050915.2657694-1-anshuman.khandual@arm.comSigned-off-by: Will Deacon <will@kernel.org>