mfd: tps65217: Fix nonstandard declaration

The tps65217 gained a new warning when building with W=1:

drivers/mfd/tps65217.c:85:1: error: 'inline' is not at beginning of declaration [-Werror=old-style-declaration]

This fixes it by putting the 'inline' modifier before 'const'.

Fixes: 262d5cc6ceb2 ("mfd: tps65217: Add support for IRQs")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Lee Jones <lee.jones@linaro.org>