phy: samsung: unify naming and describe driver in KConfig

We use everywhere "Samsung" and "Exynos", not the uppercase versions.
Describe better which driver applies to which SoC, to make configuring
kernel for Samsung SoC easier.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210924132658.109814-1-krzysztof.kozlowski@canonical.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>