arm64: Kconfig: Enable LSE atomics by default

Now that we're seeing CPUs shipping with LSE atomics, default them to
'on' in Kconfig. CPUs without the instructions will continue to use
LDXR/STXR-based sequences, but they will be placed out-of-line by the
compiler.
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/Kconfig

@@ -1051,6 +1051,7 @@ config ARM64_PAN
 
 config ARM64_LSE_ATOMICS
 	bool "Atomic instructions"
+	default y
 	help
 	  As part of the Large System Extensions, ARMv8.1 introduces new
 	  atomic instructions that are designed specifically to scale in
@@ -1059,7 +1060,8 @@ config ARM64_LSE_ATOMICS
 	  Say Y here to make use of these instructions for the in-kernel
 	  atomic routines. This incurs a small overhead on CPUs that do
 	  not support these instructions and requires the kernel to be
-	  built with binutils >= 2.25.
+	  built with binutils >= 2.25 in order for the new instructions
+	  to be used.
 
 config ARM64_VHE
 	bool "Enable support for Virtualization Host Extensions (VHE)"