audio: pcm_converter: add ARM Cortex-M DSP format conversion routines

Implement ARM Cortex-M DSP optimizations for PCM format conversion:
- Add CONFIG_FORMAT_CONVERT_ARM_SIMD Kconfig option in audio Kconfig.
- Define PCM_CONVERTER_ARM_SIMD in pcm_converter.h.
- Implement pcm_converter_arm.c:
  * Fast integer format conversions (S16, S24, S32) using SXTH,
    PKHBT, SSAT, and sign extension.
  * Float-to-integer and integer-to-float conversions with hardware FPU.
  * Linear and circular buffer conversion routines with IPC3 and IPC4
    dispatch tables (pcm_func_map, pcm_func_vc_map).

Signed-off-by: Liam Girdwood <lgirdwood@gmail.com>

Author: lgirdwood

src/audio/Kconfig

@@ -282,6 +282,13 @@ config FORMAT_CONVERT_HIFI3
 	help
 	  Use HIFI3 extensions for optimized format conversion (experimental).
 
+config FORMAT_CONVERT_ARM_SIMD
+	bool "ARM SIMD optimized conversion"
+	default y
+	depends on ARM
+	help
+	  Use ARMv7E-M DSP and SIMD instructions for optimized format conversion.
+
 config PCM_CONVERTER_FORMAT_U8
 	bool "Support U8"
 	help

src/audio/pcm_converter/CMakeLists.txt

@@ -3,7 +3,8 @@
 add_local_sources(sof
 	pcm_converter.c
 	pcm_converter_generic.c
-	pcm_converter_hifi3.c)
+	pcm_converter_hifi3.c
+	pcm_converter_arm.c)
 
 if(CONFIG_PCM_REMAPPING_CONVERTERS)
 	add_local_sources(sof pcm_remap.c)