gpio: xlp: Update for ARCH_THUNDER2

ARCH_VULCAN arm64 platform (for Broadcom Vulcan ARM64 processors) has
been discontinued. Cavium's ThunderX2 CN99XX (ARCH_THUNDER2) will be
the next revision of this platform.

Update compile dependencies and ACPI ID to reflect this change.

Signed-off-by: Jayachandran C <jnair@caviumnetworks.com>
[Drop depreciation of ARCH_VULCAN]
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>