cris: Fix section mismatches in architecture startup code

Section mismatches can now result in build failures.
As result, cris:allnoconfig fails to build as follows.

WARNING: modpost: Found 7 section mismatch(es).
To see full details build your kernel with:
'make CONFIG_DEBUG_SECTION_MISMATCH=y'
FATAL: modpost: Section mismatches detected.
Set CONFIG_SECTION_MISMATCH_WARN_ONLY=y to allow them.

Part of the problem is that references from .text to .init.text
are not permitted, and such references are used in cris startup code.
Since references from .head.text to .init.text are permitted, move
cris startup code to a new section .head.text.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Jesper Nilsson <jesper.nilsson@axis.com>