Get rid of .car.global_data warnings for GCC build

Get rid of .car.global_data warnings for GCC build

The "used" attribute was added in commit 27cf2472 which caused these
warnings to start appearing when using the standard coreboot GCC
toolchain:

{standard input}: Assembler messages:
{standard input}:96: Warning: ignoring changed section type for .car.global_data
{standard input}:96: Warning: ignoring changed section attributes for
.car.global_data

The # at the end of the section name causes the assembler to
ignore everything following the name. I verified that the resulting
binaries are the same with and without the #.

Change-Id: Iaac8042533842ed887f33895f083b613a18f496a
Signed-off-by: Martin Roth <gaumless@gmail.com>
Reviewed-on: http://review.coreboot.org/8301
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@google.com>