irqchip/mbigen: Repair non-kernel-doc notation

Fix kernel-doc warnings in irq-mbigen.c:

irq-mbigen.c:29: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
* In mbigen vector register
irq-mbigen.c:43: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
* offset of clear register in mbigen node
irq-mbigen.c:50: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
* offset of interrupt type register

Signed-off-by: Randy Dunlap <[e-mail]>
Reported-by: kernel test robot <[e-mail]>
Cc: Jun Ma <[e-mail]>
Cc: Yun Wu <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Marc Zyngier <[e-mail]>
Cc: Aditya Srivastava <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/irqchip/irq-mbigen.c

···
 /* The maximum IRQ pin number of mbigen chip(start from 0) */
 #define MAXIMUM_IRQ_PIN_NUM		1407
 
-/**
+/*
  * In mbigen vector register
  * bit[21:12]:	event id value
  * bit[11:0]:	device id
···
 /* offset of vector register in mbigen node */
 #define REG_MBIGEN_VEC_OFFSET		0x200
 
-/**
+/*
  * offset of clear register in mbigen node
  * This register is used to clear the status
  * of interrupt
  */
 #define REG_MBIGEN_CLEAR_OFFSET		0xa000
 
-/**
+/*
  * offset of interrupt type register
  * This register is used to configure interrupt
  * trigger type