mtd: spi-nor: scale up timeout for full-chip erase

This patch fixes timeout issues seen on large NOR flash.
For full-chip erase, where we use the SPINOR_OP_CHIP_ERASE (0xc7)
opcode. Use a different timeout for full-chip erase than for other
commands.

 [Ported from Linux kernel commit
                09b6a377687b ("mtd: spi-nor: scale up timeout for
                               full-chip erase") ]

Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu@amd.com>