MIPS: Remove "weak" from get_c0_fdc_int() declaration

Weak header file declarations are error-prone because they make every
definition weak, and the linker chooses one based on link order (see
10629d71 ("PCI: Remove __weak annotation from pcibios_get_phb_of_node
decl")).

The most elegant solution is to have a weak default implementation and
allow a strong function to override it.  Then we don't have to test
whether a definition is present, and if there are ever multiple strong
definitions, we get a link error instead of calling a random definition.

Add a weak get_c0_fdc_int() definition with the default code and remove the
weak annotation from the declaration.
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: James Hogan <james.hogan@imgtec.com>
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/10687/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/irq.h

@@ -49,7 +49,7 @@ extern int cp0_compare_irq_shift;
 extern int cp0_perfcount_irq;
 extern int cp0_fdc_irq;
 
-extern int __weak get_c0_fdc_int(void);
+extern int get_c0_fdc_int(void);
 
 void arch_trigger_all_cpu_backtrace(bool);
 #define arch_trigger_all_cpu_backtrace arch_trigger_all_cpu_backtrace

drivers/tty/mips_ejtag_fdc.c

@@ -879,6 +879,11 @@ static const struct tty_operations mips_ejtag_fdc_tty_ops = {
 	.chars_in_buffer	= mips_ejtag_fdc_tty_chars_in_buffer,
 };
 
+int __weak get_c0_fdc_int(void)
+{
+	return -1;
+}
+
 static int mips_ejtag_fdc_tty_probe(struct mips_cdmm_device *dev)
 {
 	int ret, nport;
@@ -967,8 +972,6 @@ static int mips_ejtag_fdc_tty_probe(struct mips_cdmm_device *dev)
 	wake_up_process(priv->thread);
 
 	/* Look for an FDC IRQ */
-	priv->irq = -1;
-	if (get_c0_fdc_int)
 	priv->irq = get_c0_fdc_int();
 
 	/* Try requesting the IRQ */