drm/i915/gvt: verify functions types in new_mmio_info()

The current prototype of new_mmio_info() uses void* for parameters read
and write, which are functions with precise calling conventions
(argument types and return type). Write down these conventions in
new_mmio_info() definition.

This has been reported by the following warnings when clang is used to
build the kernel:

    drivers/gpu/drm/i915/gvt/handlers.c:124:21: error: pointer type
    mismatch ('void *' and 'int (*)(struct intel_vgpu *, unsigned int,
    void *, unsigned int)') [-Werror,-Wpointer-type-mismatch]
            info->read = read ? read : intel_vgpu_default_mmio_read;
                              ^ ~~~~   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    drivers/gpu/drm/i915/gvt/handlers.c:125:23: error: pointer type
    mismatch ('void *' and 'int (*)(struct intel_vgpu *, unsigned int,
    void *, unsigned int)') [-Werror,-Wpointer-type-mismatch]
            info->write = write ? write : intel_vgpu_default_mmio_write;
                                ^ ~~~~~   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This allows the compiler to detect that sbi_ctl_mmio_write() returns a
"bool" value instead of an expected "int" one. Fix this.
Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

drivers/gpu/drm/i915/gvt/handlers.c

@@ -93,7 +93,8 @@ static void write_vreg(struct intel_vgpu *vgpu, unsigned int offset,
 static int new_mmio_info(struct intel_gvt *gvt,
 		u32 offset, u32 flags, u32 size,
 		u32 addr_mask, u32 ro_mask, u32 device,
-		void *read, void *write)
+		int (*read)(struct intel_vgpu *, unsigned int, void *, unsigned int),
+		int (*write)(struct intel_vgpu *, unsigned int, void *, unsigned int))
 {
 	struct intel_gvt_mmio_info *info, *p;
 	u32 start, end, i;
@@ -974,7 +975,7 @@ static int sbi_data_mmio_read(struct intel_vgpu *vgpu, unsigned int offset,
 	return 0;
 }
 
-static bool sbi_ctl_mmio_write(struct intel_vgpu *vgpu, unsigned int offset,
+static int sbi_ctl_mmio_write(struct intel_vgpu *vgpu, unsigned int offset,
 		void *p_data, unsigned int bytes)
 {
 	u32 data;