fix gcc compiling error

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@1265 bbd45198-f89e-11dd-88c7-29a3b14d5316

libcpu/arm/lm3s/context_gcc.S

@@ -146,9 +146,9 @@ rt_hw_context_switch_to:
 	/* set the PendSV exception priority */
 	LDR	r0, =NVIC_SYSPRI2
 	LDR	r1, =NVIC_PENDSV_PRI
-	LDR.W   R2, [r0,#0x00]          ; read
-	ORR     r1,r1,r2                ; modify
-    STR     r1, [r0]                ; write-bak
+	LDR.W   R2, [r0,#0x00]          /* read */
+	ORR     r1,r1,r2                /* modify */
+    	STR     r1, [r0]                /* write-back */
 
 	LDR	r0, =NVIC_INT_CTRL      /* trigger the PendSV exception (causes context switch) */
 	LDR	r1, =NVIC_PENDSVSET