Update segment sizes for user code and data

[sudoheckbeluga]

No description provided.

[sai-kaushik-s]

The SEG macro performs (lim) >> 12 internally. This shift is done because the granularity bit (g) is set to 1, which tells the CPU to interpret the limit in units of 4KB pages. If PROCSIZE << 12 = 0x100000000 is passed and uint is 32-bit, this overflows to 0. The resulting segment would have a limit of 0, meaning it could only access 4KB.