gpio: xlp: update GPIO_XLP dependency

Broadcom Vulcan (ARCH_VULCAN) has been discontinued and will be deleted
soon. So, update the GPIO_XLP Kconfig entry to remove the ARCH_VULCAN
dependency.

Also update the documentation to note that Cavium ThunderX2 uses this
driver.
Signed-off-by: NJayachandran C <jnair@caviumnetworks.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

drivers/gpio/Kconfig

@@ -504,12 +504,13 @@ config GPIO_XILINX
 
 config GPIO_XLP
 	tristate "Netlogic XLP GPIO support"
-	depends on OF_GPIO && (CPU_XLP || ARCH_VULCAN || ARCH_THUNDER2 || COMPILE_TEST)
+	depends on OF_GPIO && (CPU_XLP || ARCH_THUNDER2 || COMPILE_TEST)
 	select GPIOLIB_IRQCHIP
 	help
 	  This driver provides support for GPIO interface on Netlogic XLP MIPS64
 	  SoCs. Currently supported XLP variants are XLP8XX, XLP3XX, XLP2XX,
-	  XLP9XX and XLP5XX.
+	  XLP9XX and XLP5XX. The same GPIO controller block is also present in
+	  Cavium's ThunderX2 CN99XX SoCs.
 
 	  If unsure, say N.