refactor(gicv3): add helper function to get the limit of SPI INTID

Add helper function gicv3_get_spi_limit() to get the value of (maximum
SPI INTID + 1), so that some duplicated code can be removed later.

Signed-off-by: Heyi Guo <guoheyi@linux.alibaba.com>
Change-Id: I160c8a88fbb71d22790b8999a84afbfba766f5e7
diff --git a/drivers/arm/gic/v3/gicv3_private.h b/drivers/arm/gic/v3/gicv3_private.h
index 416cdd0..7965f40 100644
--- a/drivers/arm/gic/v3/gicv3_private.h
+++ b/drivers/arm/gic/v3/gicv3_private.h
@@ -233,6 +233,7 @@
 /*******************************************************************************
  * Private GICv3 helper function prototypes
  ******************************************************************************/
+unsigned int gicv3_get_spi_limit(uintptr_t gicd_base);
 void gicv3_spis_config_defaults(uintptr_t gicd_base);
 void gicv3_ppi_sgi_config_defaults(uintptr_t gicr_base);
 unsigned int gicv3_secure_ppi_sgi_config_props(uintptr_t gicr_base,