Revert 518adcca0a and dbe232e24e

518adcca0a: "Try using arm32 implementation for fibers."
dbe232e24e: "Order of arguments might be incorrect in arm32 coroutine implementation."

It seems to cause SEGV consistently on Ubuntu armv7l eabihf:

https://rubyci.org/logs/rubyci.s3.amazonaws.com/scw-9d6766/ruby-master/log/20190625T081710Z.fail.html.gz
https://rubyci.org/logs/rubyci.s3.amazonaws.com/scw-9d6766/ruby-master/log/20190625T111708Z.fail.html.gz

configure.ac

@@ -2272,9 +2272,6 @@ AS_CASE(["$rb_cv_fiber_coroutine"], [yes|''], [
         [x64-mingw32], [
             rb_cv_fiber_coroutine=win64
         ],
-        [armv7*-linux-*], [
-            rb_cv_fiber_coroutine=arm32
-        ],
         [aarch64-linux], [
             rb_cv_fiber_coroutine=arm64
         ],

coroutine/arm32/Context.S

@@ -9,10 +9,6 @@
 
 .globl coroutine_transfer
 coroutine_transfer:
-	stmia r0!, {r4-r11,sp,lr}
-	ldmia r1!, {r4-r11,sp,pc}
+	stmia r1!, {r4-r11,sp,lr}
+	ldmia r0!, {r4-r11,sp,pc}
 	bx lr
-
-#if defined(__linux__) && defined(__ELF__)
-.section .note.GNU-stack,"",%progbits
-#endif