Update interrupts to be masked when accessing flash (#1388)

Author: igrr

cores/esp8266/Esp.cpp

@@ -466,7 +466,15 @@ bool EspClass::updateSketch(Stream& in, uint32_t size, bool restartOnFail, bool
     return true;
 }
 
-static const int FLASH_INT_MASK = ((B10 << 8) | B00111010);
+// Interrupts which are masked by flash access routines
+static const int FLASH_INT_MASK =
+    (1 << ETS_SLC_INUM) |
+    (1 << ETS_SPI_INUM) |
+    (1 << ETS_GPIO_INUM) |
+    (1 << ETS_UART_INUM) |
+    (1 << ETS_CCOMPARE0_INUM) |
+    (1 << ETS_FRC_TIMER1_INUM);
+    
 
 bool EspClass::flashEraseSector(uint32_t sector) {
     ets_isr_mask(FLASH_INT_MASK);