MIPS: BMIPS: Fix compilation for BMIPS5000

Commit 02b849f7 ("MIPS: Get rid of the
use of .macro in C code.") replaced the macro usage but missed
the accessors in bmips.h, causing the following build error:

  CC      arch/mips/kernel/smp-bmips.o
{standard input}: Assembler messages:
{standard input}:951: Error: Unrecognized opcode `_ssnop'
{standard input}:952: Error: Unrecognized opcode `_ssnop'
(...)
make[6]: *** [arch/mips/kernel/smp-bmips.o] Error 1

Fix by rewriting the inline assembler using existing inline functions.
The generated code should stay unchanged.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/5644/Reviewed-by: Jonas Gorski <jogo@openwrt.org>

arch/mips/include/asm/bmips.h

@@ -65,44 +65,33 @@ static inline unsigned long bmips_read_zscm_reg(unsigned int offset)
 {
 	unsigned long ret;
 
-	__asm__ __volatile__(
-		".set push\n"
-		".set noreorder\n"
-		"cache %1, 0(%2)\n"
-		"sync\n"
-		"_ssnop\n"
-		"_ssnop\n"
-		"_ssnop\n"
-		"_ssnop\n"
-		"_ssnop\n"
-		"_ssnop\n"
-		"_ssnop\n"
-		"mfc0 %0, $28, 3\n"
-		"_ssnop\n"
-		".set pop\n"
-		: "=&r" (ret)
-		: "i" (Index_Load_Tag_S), "r" (ZSCM_REG_BASE + offset)
-		: "memory");
+	barrier();
+	cache_op(Index_Load_Tag_S, ZSCM_REG_BASE + offset);
+	__sync();
+	_ssnop();
+	_ssnop();
+	_ssnop();
+	_ssnop();
+	_ssnop();
+	_ssnop();
+	_ssnop();
+	ret = read_c0_ddatalo();
+	_ssnop();
+
 	return ret;
 }
 
 static inline void bmips_write_zscm_reg(unsigned int offset, unsigned long data)
 {
-	__asm__ __volatile__(
-		".set push\n"
-		".set noreorder\n"
-		"mtc0 %0, $28, 3\n"
-		"_ssnop\n"
-		"_ssnop\n"
-		"_ssnop\n"
-		"cache %1, 0(%2)\n"
-		"_ssnop\n"
-		"_ssnop\n"
-		"_ssnop\n"
-		: /* no outputs */
-		: "r" (data),
-		  "i" (Index_Store_Tag_S), "r" (ZSCM_REG_BASE + offset)
-		: "memory");
+	write_c0_ddatalo(data);
+	_ssnop();
+	_ssnop();
+	_ssnop();
+	cache_op(Index_Store_Tag_S, ZSCM_REG_BASE + offset);
+	_ssnop();
+	_ssnop();
+	_ssnop();
+	barrier();
 }
 
 #endif /* !defined(__ASSEMBLY__) */