Merge branch 'bugfix/uart_isr_rodata' into 'master'

UART driver: Fix crash in ISR due to "UART" static array moved to flash



Ref: http://esp32.com/viewtopic.php?f=13&t=546&sid=76ff371ae2b259441a2cf355e96d74b9#p2275



This is a really subtle bug, gcc noticed the UART array elements are read-only so

implicitly moved the elements to .rodata as if it was const. However

this array is accessed from the UART ISR, so has to be in IRAM or DRAM.



See merge request !245

components/driver/uart.c

@@ -84,7 +84,8 @@ typedef struct {
 
 
 static uart_obj_t *p_uart_obj[UART_NUM_MAX] = {0};
-static uart_dev_t* UART[UART_NUM_MAX] = {&UART0, &UART1, &UART2};
+/* DRAM_ATTR is required to avoid UART array placed in flash, due to accessed from ISR */
+static DRAM_ATTR uart_dev_t* const UART[UART_NUM_MAX] = {&UART0, &UART1, &UART2};
 static portMUX_TYPE uart_spinlock[UART_NUM_MAX] = {portMUX_INITIALIZER_UNLOCKED, portMUX_INITIALIZER_UNLOCKED, portMUX_INITIALIZER_UNLOCKED};
 
 esp_err_t uart_set_word_length(uart_port_t uart_num, uart_word_length_t data_bit)