ARCv2: save r30 on kernel entry as gcc uses it for code-gen

This is not exposed to userspace debugers yet, which can be done
independently as a seperate patch !
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/include/asm/entry-arcv2.h

@@ -16,6 +16,7 @@
 	;
 	; Now manually save: r12, sp, fp, gp, r25
 
+	PUSH	r30
 	PUSH	r12
 
 	; Saving pt_regs->sp correctly requires some extra work due to the way
@@ -72,6 +73,7 @@
 	POPAX	AUX_USER_SP
 1:
 	POP	r12
+	POP	r30
 
 .endm
 

arch/arc/include/asm/ptrace.h

@@ -84,7 +84,7 @@ struct pt_regs {
 	unsigned long fp;
 	unsigned long sp;	/* user/kernel sp depending on where we came from  */
 
-	unsigned long r12;
+	unsigned long r12, r30;
 
 	/*------- Below list auto saved by h/w -----------*/
 	unsigned long r0, r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11;