docs(ppa): add a note about bilinear scaling algorithm in PPA SRM

Closes https://github.com/espressif/esp-idf/issues/17531

docs/en/api-reference/peripherals/ppa.rst

@@ -93,6 +93,10 @@ Some notes to avoid confusion in configuring :cpp:type:`ppa_srm_oper_config_t`:
     - Output block's width/height is totally determined by the input block's width/height, scaling factor, and rotation angle, so output block's width/height does not need to be configured. However, please make sure the output block can fit at the offset location in the output picture.
     - If the color mode of the input or output picture is ``PPA_SRM_COLOR_MODE_YUV420``, then its ``pic_w``, ``pic_h``, ``block_w``, ``block_h``, ``block_offset_x``, ``block_offset_y`` fields must be even.
 
+.. note::
+
+    The PPA SRM internally uses bilinear scaling algorithm to process. Therefore, it may cause chromatic aberration and loss of contrast at the edges in a scaled picture.
+
 Blend
 ~~~~~
 

docs/zh_CN/api-reference/peripherals/ppa.rst

@@ -93,6 +93,10 @@ PPA 操作包括：
     - 输出块的宽度/高度完全由输入块的宽度/高度、缩放因子和旋转角度决定，因此无需配置输出块的宽度/高度。但请确保输出块可以适应输出图片中的偏移位置。
     - 如果输入或输出图片的色彩模式为 ``PPA_SRM_COLOR_MODE_YUV420``，那么其 ``pic_w``、``pic_h``、``block_w``、``block_h``、``block_offset_x`` 以及 ``block_offset_y`` 字段必须为偶数。
 
+.. note::
+
+    PPA SRM 内部使用双线性缩放算法进行处理。因此，缩放后的图片边缘可能会出现色差和对比度损失。
+
 叠加
 ~~~~