csky: Fixup remove unnecessary save/restore PSR code

All processes' PSR could success from SETUP_MMU, so need set it
in INIT_THREAD again.

And use a3 instead of r7 in __switch_to for code convention.
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>

arch/csky/include/asm/processor.h

@@ -42,7 +42,6 @@ extern struct cpuinfo_csky cpu_data[];
 
 struct thread_struct {
 	unsigned long  ksp;       /* kernel stack pointer */
-	unsigned long  sr;        /* saved status register */
 	unsigned long  trap_no;   /* saved status register */
 
 	/* FPU regs */
@@ -51,7 +50,6 @@ struct thread_struct {
 
 #define INIT_THREAD  { \
 	.ksp = sizeof(init_stack) + (unsigned long) &init_stack, \
-	.sr = DEFAULT_PSR_VALUE, \
 }
 
 /*

arch/csky/kernel/asm-offsets.c

@@ -19,7 +19,6 @@ int main(void)
 
 	/* offsets into the thread struct */
 	DEFINE(THREAD_KSP,        offsetof(struct thread_struct, ksp));
-	DEFINE(THREAD_SR,         offsetof(struct thread_struct, sr));
 	DEFINE(THREAD_FESR,       offsetof(struct thread_struct, user_fp.fesr));
 	DEFINE(THREAD_FCR,        offsetof(struct thread_struct, user_fp.fcr));
 	DEFINE(THREAD_FPREG,      offsetof(struct thread_struct, user_fp.vr));

arch/csky/kernel/entry.S

@@ -330,9 +330,6 @@ ENTRY(__switch_to)
 	lrw	a3, TASK_THREAD
 	addu	a3, a0
 
-	mfcr	a2, psr			/* Save PSR value */
-	stw	a2, (a3, THREAD_SR)	/* Save PSR in task struct */
-
 	SAVE_SWITCH_STACK
 
 	stw	sp, (a3, THREAD_KSP)
@@ -343,12 +340,9 @@ ENTRY(__switch_to)
 
 	ldw	sp, (a3, THREAD_KSP)	/* Set next kernel sp */
 
-	ldw	a2, (a3, THREAD_SR)	/* Set next PSR */
-	mtcr	a2, psr
-
 #if  defined(__CSKYABIV2__)
-	addi	r7, a1, TASK_THREAD_INFO
-	ldw	tls, (r7, TINFO_TP_VALUE)
+	addi	a3, a1, TASK_THREAD_INFO
+	ldw	tls, (a3, TINFO_TP_VALUE)
 #endif
 
 	RESTORE_SWITCH_STACK