MIPS: retire "asm/llsc.h"

all that "asm/llsc.h" does is just to help inline asm, which can be
stringifyed from "asm/asm.h"

+. Since "asm/asm.h" has all we need, retire "asm/llsc.h"

+. remove unused header file

Inspired-by:   Maciej W. Rozycki <macro@orcam.me.uk>
Signed-off-by: Huang Pei <huangpei@loongson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/include/asm/asm.h

@@ -222,6 +222,8 @@ symbol		=	value
 #define LONG_SRLV	srlv
 #define LONG_SRA	sra
 #define LONG_SRAV	srav
+#define LONG_INS	ins
+#define LONG_EXT	ext
 
 #ifdef __ASSEMBLY__
 #define LONG		.word
@@ -249,6 +251,8 @@ symbol		=	value
 #define LONG_SRLV	dsrlv
 #define LONG_SRA	dsra
 #define LONG_SRAV	dsrav
+#define LONG_INS	dins
+#define LONG_EXT	dext
 
 #ifdef __ASSEMBLY__
 #define LONG		.dword