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

Add helper function gicv3_get_espi_limit() to get the value of
(maximum extended SPI INTID + 1), so that some duplicated code can be
removed later.

Signed-off-by: Heyi Guo <guoheyi@linux.alibaba.com>
Change-Id: I0355ca2647f872e8189add259f6c47d415494cce
diff --git a/drivers/arm/gic/v3/gicv3_private.h b/drivers/arm/gic/v3/gicv3_private.h
index 7965f40..93ee1a1 100644
--- a/drivers/arm/gic/v3/gicv3_private.h
+++ b/drivers/arm/gic/v3/gicv3_private.h
@@ -234,6 +234,7 @@
  * Private GICv3 helper function prototypes
  ******************************************************************************/
 unsigned int gicv3_get_spi_limit(uintptr_t gicd_base);
+unsigned int gicv3_get_espi_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,