libthread: rm unused ARM (get|set)mcontext (#354)

They were just a duplicate of my(get|set)mcontext from the other
assembly file, and unused from threadimpl.h.

Change-Id: Id8003e5177ed9d37a7f0210037acbe55bbf7f708

src/libthread/Linux-arm-asm.s

@@ -8,46 +8,3 @@ _tas:
 	swp	r3, r3, [r0]
 	mov	r0, r3
 	mov	pc, lr
-
-.globl getmcontext
-getmcontext:
-	str	r1, [r0,#4]
-	str	r2, [r0,#8]
-	str	r3, [r0,#12]
-	str	r4, [r0,#16]
-	str	r5, [r0,#20]
-	str	r6, [r0,#24]
-	str	r7, [r0,#28]
-	str	r8, [r0,#32]
-	str	r9, [r0,#36]
-	str	r10, [r0,#40]
-	str	r11, [r0,#44]
-	str	r12, [r0,#48]
-	str	r13, [r0,#52]
-	str	r14, [r0,#56]
-	/* store 1 as r0-to-restore */
-	mov	r1, #1
-	str	r1, [r0]
-	/* return 0 */
-	mov	r0, #0
-	mov	pc, lr
-
-.globl setmcontext
-setmcontext:
-	ldr	r1, [r0,#4]
-	ldr	r2, [r0,#8]
-	ldr	r3, [r0,#12]
-	ldr	r4, [r0,#16]
-	ldr	r5, [r0,#20]
-	ldr	r6, [r0,#24]
-	ldr	r7, [r0,#28]
-	ldr	r8, [r0,#32]
-	ldr	r9, [r0,#36]
-	ldr	r10, [r0,#40]
-	ldr	r11, [r0,#44]
-	ldr	r12, [r0,#48]
-	ldr	r13, [r0,#52]
-	ldr	r14, [r0,#56]
-	ldr	r0, [r0]
-	mov	pc, lr
-