mimxrt/boards: Fix __VECTOR_TABLE link issue with CMSIS 5.9.0.

In CMSIS 5.9.0, the compiler headers define `__VECTOR_TABLE`, which will be
substituted with its corresponding value (e.g., `__Vectors` for gcc).
However, the linker script in this port can't include compiler headers when
it's processed, so `__VECTOR_TABLE` is used as the literal variable name,
which results in an undefined linker error.

To fix this, the two possible values of `__VECTOR_TABLE` are both defined
in the linker script.

Signed-off-by: iabdalkader <i.abdalkader@gmail.com>

ports/mimxrt/boards/common.ld

@@ -83,13 +83,14 @@ SECTIONS
   /* The startup code goes first into internal RAM */
   .interrupts :
   {
-    __VECTOR_TABLE = .;
+    __Vectors = .;
+    __vector_table = .;
     . = ALIGN(4);
     KEEP(*(.isr_vector))     /* Startup code */
     . = ALIGN(4);
   } > m_interrupts
 
-  __VECTOR_RAM = __VECTOR_TABLE;
+  __VECTOR_RAM = __Vectors;
   __RAM_VECTOR_TABLE_SIZE_BYTES = 0x0;
 
   /* The program code and other data goes into internal RAM */