soc: mt8195: Fix HAL directory name

This needs to match the Zephyr-side CONFIG_SOC_TOOLCHAIN_NAME, which
must match the toolchain prefix in the SDK, and it didn't.  It was
benign because my builds were set not to build the HAL and the
core-isa.h here is also available in the SDK toolchain.

Make them match.

Signed-off-by: Andy Ross <andyross@google.com>