am263x: uart: Fix the uart read issue

- Updated UART_fifoRead API to replace 'readSizeRemaining'
  with 'tempReadSizeRemaining' variable in the while condition.
- This is because, if we pass read characters
  more than the actual read count then tempReadSizeRemaining
  variable will become negative and returning negative value
  from UART_fifoRead API.

Fixes: MCUSDK-13439

Signed-off-by: Anil Dali <anil.dali@ti.com>

Author: Anil Dali

source/drivers/uart/v0/lld/uart_v0_lld.c

@@ -2621,7 +2621,7 @@ static uint32_t UART_fifoRead(UARTLLD_Handle hUart, uint8_t *buffer,
 
     isRxReady = UART_statusIsDataReady(hUart);
 
-    while (((Bool)TRUE == isRxReady) && (0U != readSizeRemaining))
+    while (((Bool)TRUE == isRxReady) && (0U != tempReadSizeRemaining))
     {
         /* once the H/w is ready  reading from the H/w                        */
         *tempBuffer = (UInt8) UART_readByte(hUart);