i2c: Fix filtering on alias for i2c-ram

Was previously looking for i2c_ram which is incorrect, the alias was
always i2c-ram.

Signed-off-by: Tom Burdick <[email protected]>

Author: teburd

tests/drivers/i2c/i2c_ram/testcase.yaml

@@ -3,7 +3,7 @@ common:
   tags:
     - drivers
     - i2c
-  filter: dt_alias_exists("i2c_ram")
+  filter: dt_alias_exists("i2c-ram")
 tests:
   drivers.i2c.ram:
     depends_on: i2c