drivers: firmware: psci: make two helper functions inline

drivers: firmware: psci: make two helper functions inline

The previous patch marked these two as 'static' which showed that they
are sometimes unused:

drivers/firmware/psci.c:103:13: error: 'psci_power_state_is_valid' defined but not used [-Werror=unused-function]
 static bool psci_power_state_is_valid(u32 state)
drivers/firmware/psci.c:94:13: error: 'psci_power_state_loses_context' defined but not used [-Werror=unused-function]
 static bool psci_power_state_loses_context(u32 state)

This also marks the functions 'inline', which has the main effect of
silently ignoring them when they are unused. The compiler will typically
inline small static functions anyway, so this seems more appropriate
than using __maybe_unused, which would have the same result otherwise.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 21e8868 ("drivers: firmware: psci: make two helper functions static")