msrtool: Add endptr to str2msr() showing how many characters were parsed

msrtool: Add endptr to str2msr() showing how many characters were parsed

This also introduces a small change in the user interface for immediate
mode (-i). Previously, whitespace could separate high and low words in
an MSR as such:

msrtool -i 4c00000f='f2f100ff 56960004'

That is no longer allowed, a space character now ends the MSR value. Any
other character can still be used as separator however, so the following
syntax still works as expected:

msrtool -i 4c00000f=f2f100ff:56960004

Signed-off-by: Peter Stuge <peter@stuge.se>
Acked-by: Stefan Reinauer <stepan@coresystems.de>
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@5032 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1