staging: brcm80211: remove use of si_* functions from wlc_phy_lcn.c

The source file used si_alp_clock to determine crystal frequency.
It now uses the si_pmu_alp_clock call instead to remove dependency from
siutils functionality.

Cc: devel@linuxdriverproject.org
Cc: linux-wireless@vger.kernel.org
Cc: Brett Rudley <brudley@broadcom.com>
Cc: Henry Ptasinski <henryp@broadcom.com>
Cc: Roland Vossen <rvossen@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>