Fix undefined behavior in gas/contrib/tc-arm.c's rotate_left() macro,
similar to https://svnweb.freebsd.org/base?view=revision&revision=274856

This fixes possible "invalid constant after fixup" errors from gas, when
it has been compiled with high levels of optimization.

Obtained from: binutils commit d840c081f8082e8b9e63fead5306643975a97bb3
PR: 197806
Approved by: maintainer (bapt)