alsa-info.sh: uname - reduce execs by four, and eliminate a logic bug

alsa-info.sh: uname - reduce execs by four, and eliminate a logic bug

Per `info uname`, `uname` always prints its data in the same order.
Also, "note that A && B || C is not if-then-else. C may run when A is true."
https://www.shellcheck.net/wiki/SC2015

set -x; read -r KERNEL_VERSION < <(uname -v); smp=x; \
  [[ "$KERNEL_VERSION" = *SMP* ]] && \
  { smp=y; readonly smp; false;} || smp=n; set -

  ... https://github.com/koalaman/shellcheck

Fixes: https://github.com/alsa-project/alsa-utils/pull/207
From: wileyhy @ github
Signed-off-by: Jaroslav Kysela <perex@perex.cz>