Update the NIOSII port to enable longer jumps (#578)

Update the NIOSII port so it works on systems with more RAM as
per https://forums.freertos.org/t/nios-ii-r-nios2-call26-noat-linker-error/16028

portable/GCC/NiosII/port_asm.S

@@ -76,12 +76,12 @@ save_sp_to_pxCurrentTCB:
 	ldw		et, (et)			# Load the value of the pxCurrentTCB pointer
 	stw		sp, (et)			# Store the stack pointer into the top of the TCB
 
-	br		irq_test_user					# skip the section .exceptions.entry
+	br		irq_test_user		# skip the section .exceptions.entry
 
-    .section .exceptions.irqtest, "xa"
+	.section .exceptions.irqtest, "xa"
 irq_test_user:
 
-    .section .exceptions.exit.user, "xa"
+	.section .exceptions.exit.user, "xa"
 restore_sp_from_pxCurrentTCB:
 	movia	et, pxCurrentTCB		# Load the address of the pxCurrentTCB pointer
 	ldw		et, (et)				# Load the value of the pxCurrentTCB pointer
@@ -120,7 +120,7 @@ restore_context:
 	ldw		fp, 112(sp)
 	addi	sp,	sp, 116		# Release stack space
 
-    eret					# Return to address ea, loading eStatus into Status.
+	eret					# Return to address ea, loading eStatus into Status.
 
 	.section .exceptions.soft, "xa"
 soft_exceptions:
@@ -131,7 +131,8 @@ soft_exceptions:
 
 call_scheduler:
 	stw		ea, 72(sp)						# EA is PC+4 so will skip over instruction causing exception
-	call	vTaskSwitchContext				# Pick the next context.
+	movia	r15, vTaskSwitchContext			# Pick the next context - use long call version in place of "call"
+	callr	r15
 	br		restore_sp_from_pxCurrentTCB	# Switch in the task context and restore.
 
 	.section .exceptions.unknown.user