fusee_cpp: implement sdram lp0 scratch param save

libraries/libexosphere/source/libc/libgcc_thumb_case.arch.arm.s

@@ -72,3 +72,22 @@ __gnu_thumb1_case_si:
     bx      lr
 .type __gnu_thumb1_case_si, %function
 .size __gnu_thumb1_case_si, .-__gnu_thumb1_case_si
+
+.section    .text.__gnu_thumb1_case_shi, "ax", %progbits
+.globl __gnu_thumb1_case_shi
+.align      0
+.thumb_func
+.syntax unified
+__gnu_thumb1_case_shi:
+    push    {r0, r1}
+    mov     r1, lr
+    lsrs    r1, r1, #1
+    lsls    r0, r0, #1
+    lsls    r1, r1, #1
+    ldrsh   r1, [r1, r0]
+    lsls    r1, r1, #1
+    add     lr, lr, r1
+    pop     {r0, r1}
+    bx      lr
+.type __gnu_thumb1_case_shi, %function
+.size __gnu_thumb1_case_shi, .-__gnu_thumb1_case_shi