video: fbdev: kyro: remove set but not used 'ulCoreClock'

This addresses the following gcc warning with "make W=1":

drivers/video/fbdev/kyro/STG4000InitDevice.c: In function
‘SetCoreClockPLL’:
drivers/video/fbdev/kyro/STG4000InitDevice.c:247:6: warning: variable
‘ulCoreClock’ set but not used [-Wunused-but-set-variable] // yanaijie
fixed
247 | u32 ulCoreClock;
| ^~~~~~~~~~~

Reported-by: Hulk Robot <[e-mail]>
Signed-off-by: Jason Yan <[e-mail]>
[b.zolnierkie: minor patch summary fixup]
Signed-off-by: Bartlomiej Zolnierkiewicz <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/video/fbdev/kyro/STG4000InitDevice.c

···
 {
 	u32 F, R, P;
 	u16 core_pll = 0, sub;
-	u32 ulCoreClock;
 	u32 tmp;
 	u32 ulChipSpeed;
 
···
 	if (ulChipSpeed == 0)
 		return -EINVAL;
 
-	ulCoreClock = ProgramClock(REF_FREQ, CORE_PLL_FREQ, &F, &R, &P);
+	ProgramClock(REF_FREQ, CORE_PLL_FREQ, &F, &R, &P);
 
 	core_pll |= ((P) | ((F - 2) << 2) | ((R - 2) << 11));