omap: sram: fix is_sram_locked check

For OMAP24xx/34xx/44xx: omap_type() returns the correct type:
 OMAP2_DEVICE_TYPE_TEST
 OMAP2_DEVICE_TYPE_EMU
 OMAP2_DEVICE_TYPE_SEC
 OMAP2_DEVICE_TYPE_GP
 OMAP2_DEVICE_TYPE_BAD

In current implementation there are two problems:
Problem 1:
For 34xx, the current if check will never return true.

Problem 2:
For 24xx the correct type check should be with omap_type() function
Verified by checking the TRM 24xx for CONTROL_STATUS register bits

Signed-off-by: Vikram Pandita <vikram.pandita@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>