feat(fgt2): add support for FEAT_FGT2

This patch disables trapping to EL3 when the FEAT_FGT2
specific trap registers are accessed by setting the
SCR_EL3.FGTEn2 bit

Signed-off-by: Arvind Ram Prakash <arvind.ramprakash@arm.com>
Change-Id: I6d2b614affb9067b2bc3d7bf0ae7d169d031592a
diff --git a/docs/getting_started/build-options.rst b/docs/getting_started/build-options.rst
index c9c92fd..f59303e 100644
--- a/docs/getting_started/build-options.rst
+++ b/docs/getting_started/build-options.rst
@@ -346,6 +346,13 @@
    This flag can take the values 0 to 2, to align  with the ``ENABLE_FEAT``
    mechanism. Default value is ``0``.
 
+-  ``ENABLE_FEAT_FGT2``: Numeric value to enable support for FGT2
+   (Fine Grain Traps 2) feature allowing for access to Fine-grained trap 2 registers
+   during  EL2 to EL3 context save/restore operations.
+   Its an optional architectural feature and is available from v8.8 and upwards.
+   This flag can take the values 0 to 2, to align  with the ``ENABLE_FEAT``
+   mechanism. Default value is ``0``.
+
 -  ``ENABLE_FEAT_HCX``: Numeric value to set the bit SCR_EL3.HXEn in EL3 to
    allow access to HCRX_EL2 (extended hypervisor control register) from EL2 as
    well as adding HCRX_EL2 to the EL2 context save/restore operations. Its a