setarch: add support for '-R' (disable randomization)

setarch: add support for '-R' (disable randomization)

This commit adds support for the -R flag of setarch, which disables
randomization of the virtual address space.

function                                             old     new   delta
setarch_main                                         115     150     +35
packed_usage                                       30664   30651     -13

Signed-off-by: Jan Heylen <heyleke@gmail.com>
Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>