GIC: Add API to set priority mask

API documentation updated.

Change-Id: I40feec1fe67a960d035061b54dd55610bc34ce1d
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
diff --git a/include/lib/aarch32/arch_helpers.h b/include/lib/aarch32/arch_helpers.h
index c8caea28..469e9b0 100644
--- a/include/lib/aarch32/arch_helpers.h
+++ b/include/lib/aarch32/arch_helpers.h
@@ -213,6 +213,7 @@
 DEFINE_SYSOP_TYPE_FUNC(dsb, ish)
 DEFINE_SYSOP_TYPE_FUNC(dsb, ishst)
 DEFINE_SYSOP_TYPE_FUNC(dmb, ish)
+DEFINE_SYSOP_TYPE_FUNC(dmb, ishst)
 DEFINE_SYSOP_FUNC(isb)
 
 void __dead2 smc(uint32_t r0, uint32_t r1, uint32_t r2, uint32_t r3,