Make sure the psram_io struct is initialized

Closes https://github.com/espressif/esp-idf/issues/3591

components/esp32/spiram_psram.c

@@ -616,7 +616,7 @@ psram_size_t psram_get_size()
  */
 esp_err_t IRAM_ATTR psram_enable(psram_cache_mode_t mode, psram_vaddr_mode_t vaddrmode)   //psram init
 {
-    psram_io_t psram_io;
+    psram_io_t psram_io={0};
     uint32_t chip_ver = REG_GET_FIELD(EFUSE_BLK0_RDATA3_REG, EFUSE_RD_CHIP_VER_PKG);
     uint32_t pkg_ver = chip_ver & 0x7;
     if (pkg_ver == EFUSE_RD_CHIP_VER_PKG_ESP32D2WDQ5) {