MIPS: Malta: Implement get_c0_fdc_int()

Implement the weak get_c0_fdc_int() function for Malta. The Fast Debug
Channel (FDC) interrupt is obtained mainly depending on whether a GIC is
present. Vectored external interrupt mode isn't yet supported.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/9143/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/mti-malta/malta-time.c

@@ -115,6 +115,22 @@ void read_persistent_clock(struct timespec *ts)
 	ts->tv_nsec = 0;
 }
 
+int get_c0_fdc_int(void)
+{
+	int mips_cpu_fdc_irq;
+
+	if (cpu_has_veic)
+		mips_cpu_fdc_irq = -1;
+	else if (gic_present)
+		mips_cpu_fdc_irq = gic_get_c0_fdc_int();
+	else if (cp0_fdc_irq >= 0)
+		mips_cpu_fdc_irq = MIPS_CPU_IRQ_BASE + cp0_fdc_irq;
+	else
+		mips_cpu_fdc_irq = -1;
+
+	return mips_cpu_fdc_irq;
+}
+
 int get_c0_perfcount_int(void)
 {
 	if (cpu_has_veic) {