spi_flash: replace flash clock src change API with mspi timing API

components/spi_flash/include/esp_private/spi_flash_os.h

@@ -246,16 +246,7 @@ extern const spi_flash_guard_funcs_t g_flash_guard_no_os_ops;
  */
 void spi_flash_rom_impl_init(void);
 
-#if SOC_MEMSPI_CLOCK_IS_INDEPENDENT
-/**
- * @brief This functions is used to change spi flash clock source between PLL and others, which is used after system wake up from a low power mode or
- * enter low-power mode like sleep.
- * @param clk_src mspi(flash) clock source.
- *
- * @note Only called in startup. User should not call this function.
- */
-void spi_flash_set_clock_src(soc_periph_mspi_clk_src_t clk_src);
-#endif
+
 
 #ifdef __cplusplus
 }