ARM: add missing linker section markup to head-common.S

Macro __INIT is used to place various code in head-common.S into the init
section. This should be matched by a closing __FINIT. Also, add an
explicit ".text" to ensure subsequent code is placed into the correct
section; __FINIT is simply a closing marker to match __INIT and doesn't
guarantee to revert to .text.

This historically caused no problem, because macro __CPUINIT was used at
the exact location where __FINIT was missing, which then placed following
code into the cpuinit section. However, with commit 22f0a2736 "init.h:
remove __cpuinit sections from the kernel" applied, __CPUINIT becomes a
no-op, thus leaving all this code in the init section, rather than the
regular text section. This caused issues such as secondary CPU boot
failures or crashes.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
v3: Added .text after __FINIT to force the correct section.
v2: Moved __FINIT after lookup_processor_type, to correctly match the
location of __CPUINIT.
Revert "clocksource: Add generic dummy timer driver"

This reverts commit 064706514ec3fea740c2656e03c4f01f6a551ac4.