After the recent removal of the fb.h include from backlight.h, which
transitively included of.h, there are several errors from
via-pmu-backlight.c (errors from bl_curve not being properly defined
omitted):

   drivers/macintosh/via-pmu-backlight.c:22:20: error: 'FB_BACKLIGHT_LEVELS' undeclared here (not in a function)
      22 | static u8 bl_curve[FB_BACKLIGHT_LEVELS];
         |                    ^~~~~~~~~~~~~~~~~~~
   drivers/macintosh/via-pmu-backlight.c: In function 'pmu_backlight_get_level_brightness':
   drivers/macintosh/via-pmu-backlight.c:63:38: error: 'FB_BACKLIGHT_MAX' undeclared (first use in this function); did you mean 'BACKLIGHT_RAW'?
      63 |         pmulevel = bl_curve[level] * FB_BACKLIGHT_MAX / MAX_PMU_LEVEL;
         |                                      ^~~~~~~~~~~~~~~~
         |                                      BACKLIGHT_RAW
   drivers/macintosh/via-pmu-backlight.c: In function 'pmu_backlight_init':
   drivers/macintosh/via-pmu-backlight.c:144:17: error: implicit declaration of function 'of_machine_is_compatible' [-Wimplicit-function-declaration]
     144 |                 of_machine_is_compatible("AAPL,3400/2400") ||
         |                 ^~~~~~~~~~~~~~~~~~~~~~~~

FB_BACKLIGHT_{LEVELS,MAX} are available from the userspace API fb.h so
just include that avoid dragging in the full fb.h header unnecessarily.
Include linux/of.h for of_machine_is_compatible().

Fixes: 9f218f9bb9d2 ("backlight: Do not include <linux/fb.h> in header file")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
  drivers/macintosh/via-pmu-backlight.c | 2 ++
  1 file changed, 2 insertions(+)

diff --git a/drivers/macintosh/via-pmu-backlight.c b/drivers/macintosh/via-pmu-backlight.c
index 26bd9ed5e664..f7b7853b3802 100644
--- a/drivers/macintosh/via-pmu-backlight.c
+++ b/drivers/macintosh/via-pmu-backlight.c

@@ -11,7 +11,9 @@
  #include <asm/ptrace.h>
  #include <linux/adb.h>
  #include <linux/backlight.h>
+#include <linux/of.h>
  #include <linux/pmu.h>
+#include <uapi/linux/fb.h>