RISC-V: remove INTERRUPT_CAUSE_* defines from asm/irq.h

These are only of use to the local irq controller driver, so add them in
that driver implementation instead, which will be submitted soon.
Signed-off-by: NChristoph Hellwig <hch@lst.de>

arch/riscv/include/asm/irq.h

@@ -17,10 +17,6 @@
 
 #define NR_IRQS         0
 
-#define INTERRUPT_CAUSE_SOFTWARE    1
-#define INTERRUPT_CAUSE_TIMER       5
-#define INTERRUPT_CAUSE_EXTERNAL    9
-
 void riscv_timer_interrupt(void);
 
 #include <asm-generic/irq.h>