arm64: kaslr: Set TCR_EL1.NFD1 when CONFIG_RANDOMIZE_BASE=y

TCR_EL1.NFD1 was allocated by SVE and ensures that fault-surpressing SVE
memory accesses (e.g. speculative accesses from a first-fault gather load)
which translate via TTBR1_EL1 result in a translation fault if they
miss in the TLB when executed from EL0. This mitigates some timing attacks
against KASLR, where the kernel address space could otherwise be probed
efficiently using the FFR in conjunction with suppressed faults on SVE
loads.

Cc: Dave Martin <Dave.Martin@arm.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/include/asm/pgtable-hwdef.h

@@ -291,6 +291,7 @@
 #define TCR_TBI0		(UL(1) << 37)
 #define TCR_HA			(UL(1) << 39)
 #define TCR_HD			(UL(1) << 40)
+#define TCR_NFD1		(UL(1) << 54)
 
 /*
  * TTBR.