leds: LEDS_BLINK_LGM should depend on X86

The Intel Lightning Mountain (LGM) Serial Shift Output controller (SSO)
is only present on Intel Lightning Mountain SoCs.  Hence add a
dependency on X86, to prevent asking the user about this driver when
configuring a kernel without Intel Lightning Mountain platform support.

While at it, merge the other dependencies into a single statement.
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NPavel Machek <pavel@ucw.cz>

drivers/leds/blink/Kconfig

 config LEDS_LGM
        tristate "LED support for LGM SoC series"
-       depends on GPIOLIB
-       depends on LEDS_CLASS
-       depends on MFD_SYSCON
-       depends on OF
+       depends on X86 || COMPILE_TEST
+       depends on GPIOLIB && LEDS_CLASS && MFD_SYSCON && OF
        help
          This option enables support for LEDs connected to GPIO lines on
          Lightning Mountain (LGM) SoC. Lightning Mountain is a AnyWAN