STM32F2 and Particle Electron board support

CL: STM32F2 and Particle Electron board support

PUBLISHED_FROM=20dede6546e9f99d2829508177924790d87e985a

src/common/platforms/arm/arm_nsleep100_m3.S

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+/*
+ * Copyright (c) 2014-2019 Cesanta Software Limited
+ * All rights reserved
+ *
+ * Licensed under the Apache License, Version 2.0 (the ""License"");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an ""AS IS"" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+.arch armv7e-m
+.syntax unified
+.thumb
+
+/* These are required to satisfy TI linker. */
+.eabi_attribute Tag_ABI_align_needed, 1
+.eabi_attribute Tag_ABI_align_preserved, 1
+
+.global mgos_nsleep100_impl
+.global mgos_nsleep100_loop_count
+
+#ifdef STM32
+.section .RamFunc.mgos_nsleep100_impl
+#else
+.section .iram.mgos_nsleep100_impl
+#endif
+.type mgos_nsleep100_impl, %function
+.align 4
+
+mgos_nsleep100_impl:
+      ldr     r3, =mgos_nsleep100_loop_count
+      ldr     r3, [r3]
+      mul     r0, r3
+      mov     r1, #6
+      udiv    r0, r0, r1
+      cbz     r0, xxx
+lxx:
+      subs    r0, #1
+      bne     lxx
+xxx:
+      bx      lr
+.align 4
+.size mgos_nsleep100_impl, . - mgos_nsleep100_impl