arm64: Provide read/write fault information in compat signal handlers

For AArch32, bit 11 (WnR) of the FSR/ESR register is set when the fault
was caused by a write access and applications like Qemu rely on such
information being provided in sigcontext. This patch introduces the
ESR_EL1 tracking for the arm64 kernel faults and sets bit 11 accordingly
in compat sigcontext.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/include/asm/processor.h

@@ -79,6 +79,7 @@ struct thread_struct {
 	unsigned long		tp_value;
 	struct fpsimd_state	fpsimd_state;
 	unsigned long		fault_address;	/* fault info */
+	unsigned long		fault_code;	/* ESR_EL1 value */
 	struct debug_info	debug;		/* debugging */
 };