coresight: Fix compilation error

drivers/hwtracing/coresight/coresight-etm4x-core.c:2065:20: error: initialization of ‘int (*)(struct amba_device *)’ from incompatible pointer type ‘void (*)(struct amba_device *)’ [-Werror=incompatible-pointer-types]
 2065 |  .remove         = etm4_remove_amba,
      |                    ^~~~~~~~~~~~~~~~
drivers/hwtracing/coresight/coresight-etm4x-core.c:2065:20: note: (near initialization for ‘etm4x_amba_driver.remove’)

Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Change-Id: I24cf72d9ddd827fcc1a2220c1884f40e4843c335