MIPS: Add LLB bit and related feature for the Config 5 CP0 register

The LLBIT (bit 4) in the Config5 CP0 register indicates the software
availability of the Load-Linked bit. This bit is only set by hardware
and it has the following meaning:

0: LLB functionality is not supported
1: LLB functionality is supported. The following feature are also
supported:

- ERETNC instruction. Similar to ERET but it does not clear the LLB
bit in the LLAddr register.
- CP0 LLAddr/LLB bit must be set
- LLbit is software accessible through the LLAddr[0]

This will be used later on to emulate R2 LL/SC instructions.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>

arch/mips/kernel/cpu-probe.c

@@ -514,6 +514,8 @@ static inline unsigned int decode_config5(struct cpuinfo_mips *c)
 		c->options |= MIPS_CPU_EVA;
 	if (config5 & MIPS_CONF5_MRP)
 		c->options |= MIPS_CPU_MAAR;
+	if (config5 & MIPS_CONF5_LLB)
+		c->options |= MIPS_CPU_RW_LLB;
 
 	return config5 & MIPS_CONF_M;
 }