Revert of Provide THUMB version of pushAllRegisters trampoline when -mthumb is on. (https://codereview.chromium.org/163863002/)

Reason for revert:
Clang bot failing on ../../third_party/WebKit/Source/heap/asm/SaveRegisters_arm.S: Assembler messages:
../../third_party/WebKit/Source/heap/asm/SaveRegisters_arm.S:40: Error: non-constant expression in ".if"

Original issue's description:
> Provide THUMB version of pushAllRegisters trampoline when -mthumb is on.
> 
> Interworking does not seem to work correctly for component build and pushAllRegisters ends up being called from THUMB code without correct mode switch which causes SIGILL. When the whole Blink is built with -mthumb it is perfectly correct to build pushAllRegisters as thumb code as well (only r4 - r7 need to be safed).
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=167107

TBR=wibling@chromium.org,vegorov@chromium.org
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/167273002

git-svn-id: svn://svn.chromium.org/blink/trunk@167214 bbb929c8-8fbe-4397-9dbb-9b2b20218538