bios_emulator: Allow a custom interrupt handler to be installed

Sometime we want to provide an interrupt handler for the ROM, Add a
function to allow this.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/bios_emulator/include/x86emu.h b/drivers/bios_emulator/include/x86emu.h
index 278f669..63febe0 100644
--- a/drivers/bios_emulator/include/x86emu.h
+++ b/drivers/bios_emulator/include/x86emu.h
@@ -153,6 +153,7 @@
 	void X86EMU_setupMemFuncs(X86EMU_memFuncs * funcs);
 	void X86EMU_setupPioFuncs(X86EMU_pioFuncs * funcs);
 	void X86EMU_setupIntrFuncs(X86EMU_intrFuncs funcs[]);
+	void X86EMU_setupIntrFunc(int intnum, X86EMU_intrFuncs func);
 	void X86EMU_prepareForInt(int num);
 
 /* decode.c */
diff --git a/drivers/bios_emulator/x86emu/sys.c b/drivers/bios_emulator/x86emu/sys.c
index 21f9730..0ba9c0c 100644
--- a/drivers/bios_emulator/x86emu/sys.c
+++ b/drivers/bios_emulator/x86emu/sys.c
@@ -273,6 +273,11 @@
 	sys_outl = funcs->outl;
 }
 
+void X86EMU_setupIntrFunc(int intnum, X86EMU_intrFuncs func)
+{
+	_X86EMU_intrTab[intnum] = func;
+}
+
 /****************************************************************************
 PARAMETERS:
 funcs   - New interrupt vector table to make active