De-feature PL011 UART driver to match generic UART spec

The Server Base System Architecture document (ARM-DEN-0029)
specifies a generic UART device. The programmer's view of this
generic UART is a subset of the ARM PL011 UART. However, the
current PL011 driver in Trusted Firmware uses some features
that are outside the generic UART specification.

This patch modifies the PL011 driver to exclude features outside
the SBSA generic UART specification by setting the boolean build
option 'PL011_GENERIC_UART=1'. Default value is 0 (use full
PL011 features).

User guide updated.

Fixes ARM-software/tf-issues#216

Change-Id: I6e0eb86f9d69569bc3980fb57e70d6da5d91a737
diff --git a/Makefile b/Makefile
index 0c3303f..3bf9796 100644
--- a/Makefile
+++ b/Makefile
@@ -95,6 +95,8 @@
 # Flag to introduce an infinite loop in BL1 just before it exits into the next
 # image. This is meant to help debugging the post-BL2 phase.
 SPIN_ON_BL1_EXIT		:= 0
+# Build PL011 UART driver in minimal generic UART mode
+PL011_GENERIC_UART		:= 0
 
 
 ################################################################################
@@ -365,6 +367,7 @@
 $(eval $(call assert_boolean,ERROR_DEPRECATED))
 $(eval $(call assert_boolean,ENABLE_PLAT_COMPAT))
 $(eval $(call assert_boolean,SPIN_ON_BL1_EXIT))
+$(eval $(call assert_boolean,PL011_GENERIC_UART))
 
 
 ################################################################################
@@ -393,6 +396,7 @@
 ifdef EL3_PAYLOAD_BASE
 $(eval $(call add_define,EL3_PAYLOAD_BASE))
 endif
+$(eval $(call add_define,PL011_GENERIC_UART))
 
 
 ################################################################################