power panic: read whole directory name block from EEPROM

There is no need to read one byte at a time. We can simply
read the whole block in one go. This saves some flash memory.

Change in memory:
Flash: -18 bytes
SRAM: 0 bytes

Firmware/power_panic.cpp

@@ -431,9 +431,7 @@ void restore_file_from_sd()
     uint8_t depth = eeprom_read_byte((uint8_t*)EEPROM_DIR_DEPTH);
 
     for (uint8_t i = 0; i < depth; i++) {
-        for (uint8_t j = 0; j < 8; j++) {
-            dir_name[j] = eeprom_read_byte((uint8_t*)EEPROM_DIRS + j + 8 * i);
-        }
+        eeprom_read_block(dir_name, (const char *)EEPROM_DIRS + 8 * i, 8);
         dir_name[8] = '\0';
         card.chdir(dir_name, false);
     }