board: nxp: lx2160a: without QIXIS, MC-ENET, PCI, LTC3882

board: nxp: lx2160a: without QIXIS, MC-ENET, PCI, LTC3882

The shared LX2160A board file calls helpers that only exist when
their subsystem is enabled. Gate them on the matching CONFIG_*:
 - pci_init() under CONFIG_PCI.
 - fdt_fixup_mc_ddr() and fsl_rgmii_init() under CONFIG_FSL_MC_ENET.
 - qixis_*() and the QIXIS branch of checkboard() under
   CONFIG_FSL_QIXIS; cpu_name(buf) moves out so the non-QIXIS path
   still prints "Board: <name>".
 - EVENT_SPY_SIMPLE on init_func_vid moves inside the
   CONFIG_VOL_MONITOR_LTC3882_READ guard (was outside, dangling
   symbol when LTC3882 off).

 #if / #ifdef, not IS_ENABLED(), because the helpers are themselves
conditionally compiled.

While here, lx2160a_common.h: fix BOOT_TARGET_DEVICES_MMC
1 arg vs 2 args and gate the MMC target on CONFIG_CMD_MMC,
not CONFIG_MMC.

No functional change for NXP boards: LX2160ARDB, LX2160AQDS, or
LX2162AQDS, but mainly build clean up in order to support
other NXP lx2160a boards without those HW dependencies.

Signed-off-by: Vincent Jardin <vjardin@free.fr>
Signed-off-by: Peng Fan <peng.fan@nxp.com>