libbpf: Complete LoongArch (loongarch) spec in bpf_tracing.h

Add PARM6 through PARM8 definitions. Add kernel docs link describing ABI
for LoongArch.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20230120200914.3008030-10-andrii@kernel.org

tools/lib/bpf/bpf_tracing.h

@@ -316,13 +316,19 @@ struct pt_regs___arm64 {
 
 #elif defined(bpf_target_loongarch)
 
-/* https://loongson.github.io/LoongArch-Documentation/LoongArch-ELF-ABI-EN.html */
+/*
+ * https://docs.kernel.org/loongarch/introduction.html
+ * https://loongson.github.io/LoongArch-Documentation/LoongArch-ELF-ABI-EN.html
+ */
 
 #define __PT_PARM1_REG regs[4]
 #define __PT_PARM2_REG regs[5]
 #define __PT_PARM3_REG regs[6]
 #define __PT_PARM4_REG regs[7]
 #define __PT_PARM5_REG regs[8]
+#define __PT_PARM6_REG regs[9]
+#define __PT_PARM7_REG regs[10]
+#define __PT_PARM8_REG regs[11]
 #define __PT_RET_REG regs[1]
 #define __PT_FP_REG regs[22]
 #define __PT_RC_REG regs[4]