arm: mvebu: Fix function enable_caches

Commit 3308933d ("arm: mvebu: Avoid reading MVEBU_REG_PCIE_DEVID
register too many times") broke support for caches on all Armada SoCs.

Before that commit there was code:

    if (mvebu_soc_family() != MVEBU_SOC_A375) {
        dcache_enable();
    }

And after that commit there is code:

    if (IS_ENABLED(CONFIG_ARMADA_375)) {
        dcache_enable();
    }

Comment above this code says that d-cache should be disabled on Armada 375.
But new code inverted logic and broke Armada 375 and slowed down all other
Armada SoCs (including A38x).

Fix this issue by changing logic to:

    if (!IS_ENABLED(CONFIG_ARMADA_375)) {
        dcache_enable();
    }

Which matches behavior prior that commit.

Fixes: 3308933d ("arm: mvebu: Avoid reading MVEBU_REG_PCIE_DEVID register too many times")
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Marek Behún <kabel@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>