drivers/spi/tpm: Make SPI TPM driver CAR-safe

1. Use proper CAR semantics for global/static variables.
2. Use spi_* functions directly instead of using a global structure to
store pointers to those functions.

BUG=b:36873582

Change-Id: I1fc52ab797ef0cbd3793a387d68198efc5dde58c
Signed-off-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: https://review.coreboot.org/19114
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
1 file changed