zephyr: drop IS_ZEPHYR_VERSION usages from npcx espi driver
zephyr: drop IS_ZEPHYR_VERSION usages from npcx espi driver

This code was added after v2.5 was already dropped from the tree.
These macros are not necessary.

BUG=b:197159539
BRANCH=none
TEST=zmake testall

Signed-off-by: Jack Rosenthal <d3f605bef1867f59845d4ce6e4f83b8dc9e4e0ae@chromium.org>
Change-Id: Idbbf3d6431542a707f5abe954b56838a4b18403b
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3104787
Commit-Queue: Yuval Peress <50dc11c009bd4d7e9d9d15a383c1743ce5ee82ef@chromium.org>
Reviewed-by: Yuval Peress <50dc11c009bd4d7e9d9d15a383c1743ce5ee82ef@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec