Doc: Remove useless escape characters

Just like has been done in the porting guide a couple of patches
earlier, kill all escaped underscore characters in all documents.

Change-Id: I7fb5b806412849761d9221a6ce3cbd95ec43d611
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
diff --git a/docs/cpu-specific-build-macros.rst b/docs/cpu-specific-build-macros.rst
index 077d470..40128ed 100644
--- a/docs/cpu-specific-build-macros.rst
+++ b/docs/cpu-specific-build-macros.rst
@@ -93,7 +93,7 @@
 -  ``ERRATA_A53_855873``: This applies errata 855873 workaround to Cortex-A53
    CPUs. Though the erratum is present in every revision of the CPU,
    this workaround is only applied to CPUs from r0p3 onwards, which feature
-   a chicken bit in CPUACTLR\_EL1 to enable a hardware workaround.
+   a chicken bit in CPUACTLR_EL1 to enable a hardware workaround.
    Earlier revisions of the CPU have other errata which require the same
    workaround in software, so they should be covered anyway.
 
@@ -194,4 +194,4 @@
 .. _Cortex-A72 MPCore Software Developers Errata Notice: http://infocenter.arm.com/help/topic/com.arm.doc.epm012079/index.html
 .. _Firmware Design guide: firmware-design.rst
 .. _Cortex-A57 Software Optimization Guide: http://infocenter.arm.com/help/topic/com.arm.doc.uan0015b/Cortex_A57_Software_Optimization_Guide_external.pdf
-.. _Arm DSU Software Developers Errata Notice: http://infocenter.arm.com/help/topic/com.arm.doc.epm138168/index.html
\ No newline at end of file
+.. _Arm DSU Software Developers Errata Notice: http://infocenter.arm.com/help/topic/com.arm.doc.epm138168/index.html