bugfix(flash): improve spi cs timing settings for flash

cs setup time is recomemded to be 1.5T, and cs hold time is recommended to be 2.5T.
(cs_setup = 1, cs_setup_time = 0; cs_hold = 1, cs_hold_time = 1)

components/bootloader_support/src/bootloader_init.c

@@ -394,6 +394,9 @@ static void IRAM_ATTR flash_gpio_configure(const esp_image_header_t* pfhdr)
             #endif
         }
     }
+
+    // improve the flash cs timing.
+    bootloader_common_set_flash_cs_timing();
 }
 
 static void uart_console_configure(void)