stv0991: remove specific CONFIG_STV0991 configs

Remove the following STV0991 specific configs:
- CONFIG_STV0991 (never used, only defined in CONFIG_SYS_EXTRA_OPTIONS)
- CONFIG_STV0991_HZ (replaced by generic CONFIG_SYS_HZ)
- CONFIG_STV0991_HZ_CLOCK (replaced by generic CONFIG_SYS_HZ_CLOCK)

This patch allows to reduce the file config_whitelist.txt.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
diff --git a/arch/arm/include/asm/arch-stv0991/stv0991_gpt.h b/arch/arm/include/asm/arch-stv0991/stv0991_gpt.h
index cd27472..f1d5667 100644
--- a/arch/arm/include/asm/arch-stv0991/stv0991_gpt.h
+++ b/arch/arm/include/asm/arch-stv0991/stv0991_gpt.h
@@ -36,7 +36,7 @@
 #define GPT_FREE_RUNNING		0xFFFF
 
 /* Timer, HZ specific defines */
-#define CONFIG_STV0991_HZ		1000
-#define CONFIG_STV0991_HZ_CLOCK		(27*1000*1000)/GPT_PRESCALER_128
+#define CONFIG_SYS_HZ			1000
+#define CONFIG_SYS_HZ_CLOCK		((27 * 1000 * 1000) / GPT_PRESCALER_128)
 
 #endif